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DeAngelo SL, Dziechciarz S, Solanki S, Shin M, Zhao L, Balia A, El-Derany MO, Das NK, Castillo C, Bell HN, Paulo JA, Zhang Y, Rossiter NJ, McCulla EC, He J, Talukder I, Schafer ZT, Neamati N, Mancias JD, Koutmos M, Shah YM. Recharacterization of RSL3 reveals that the selenoproteome is a druggable target in colorectal cancer. bioRxiv 2024:2024.03.29.587381. [PMID: 38617233 PMCID: PMC11014488 DOI: 10.1101/2024.03.29.587381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
Ferroptosis is an iron-dependent, non-apoptotic form of cell death resulting from the accumulation of lipid peroxides. Colorectal cancer (CRC) accumulates high levels of intracellular iron and reactive oxygen species (ROS), thereby sensitizing cells to ferroptosis. The selenoprotein glutathione peroxidase (GPx4) is a key enzyme in the detoxification of lipid peroxides and can be inhibited by the compound (S)-RSL3 ([1S,3R]-RSL3). However, the stereoisomer (R)-RSL3 ([1R,3R]-RSL3), which does not inhibit GPx4, exhibits equipotent activity to (S)-RSL3 across a panel of CRC cell lines. Utilizing CRC cell lines with an inducible knockdown of GPx4, we demonstrate that (S)-RSL3 sensitivity does not align with GPx4 dependency. Subsequently, a biotinylated (S)-RSL3 was then synthesized to perform affinity purification-mass spectrometry (AP-MS), revealing that (S)-RSL3 acts as a pan-inhibitor of the selenoproteome, targeting both the glutathione and thioredoxin peroxidase systems as well as multiple additional selenoproteins. To investigate the therapeutic potential of broadly disrupting the selenoproteome as a therapeutic strategy in CRC, we employed further chemical and genetic approaches to disrupt selenoprotein function. The findings demonstrate that the selenoprotein inhibitor Auranofin can induce ferroptosis and/or oxidative cell death both in-vitro and in-vivo. Consistent with this data we observe that AlkBH8, a tRNA-selenocysteine methyltransferase required for the translational incorporation of selenocysteine, is essential for CRC growth. In summary, our research elucidates the complex mechanisms underlying ferroptosis in CRC and reveals that modulation of the selenoproteome provides multiple new therapeutic targets and opportunities in CRC.
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Affiliation(s)
- Stephen L DeAngelo
- Doctoral Program in Cancer Biology, University of Michigan Medical School, Ann Arbor, MI, United States
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, United States
| | - Sofia Dziechciarz
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Sumeet Solanki
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Myungsun Shin
- Department of Cell Biology, Harvard Medical School, Boston, MA, United States
- Dana-Farber Cancer Institute, Boston, Massachusetts, United States
| | - Liang Zhao
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Andrii Balia
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, Michigan, United States
| | - Marwa O El-Derany
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
- Department of Biochemistry, Faculty of Pharmacy, Ain Shams University, Cairo, Egypt
| | - Nupur K Das
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Cristina Castillo
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Hannah N Bell
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Joao A Paulo
- Department of Cell Biology, Harvard Medical School, Boston, MA, United States
- Dana-Farber Cancer Institute, Boston, Massachusetts, United States
| | - Yuezhong Zhang
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Nicholas J Rossiter
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, United States
| | - Elizabeth C McCulla
- Doctoral Program in Cancer Biology, University of Michigan Medical School, Ann Arbor, MI, United States
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, United States
| | - Jianping He
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
| | - Indrani Talukder
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Zachary T Schafer
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
| | - Nouri Neamati
- Department of Biochemistry, Faculty of Pharmacy, Ain Shams University, Cairo, Egypt
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, United States
| | - Joseph D Mancias
- Dana-Farber Cancer Institute, Boston, Massachusetts, United States
- Division of Radiation and Genome Stability, Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA. United States
| | - Markos Koutmos
- Department of Chemistry, University of Michigan, Ann Arbor, MI, United States
- Department of Biophysics, University of Michigan, Ann Arbor, MI, United States
| | - Yatrik M Shah
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, United States
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, United States
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2
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Wilhelm CA, Kaitany K, Kelly A, Yacoub M, Koutmos M. The protein-only RNase Ps, endonucleases that cleave pre-tRNA: Biological relevance, molecular architectures, substrate recognition and specificity, and protein interactomes. Wiley Interdiscip Rev RNA 2024; 15:e1836. [PMID: 38453211 DOI: 10.1002/wrna.1836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 01/27/2024] [Accepted: 02/06/2024] [Indexed: 03/09/2024]
Abstract
Protein-only RNase P (PRORP) is an essential enzyme responsible for the 5' maturation of precursor tRNAs (pre-tRNAs). PRORPs are classified into three categories with unique molecular architectures, although all three classes of PRORPs share a mechanism and have similar active sites. Single subunit PRORPs, like those found in plants, have multiple isoforms with different localizations, substrate specificities, and temperature sensitivities. Most recently, Arabidopsis thaliana PRORP2 was shown to interact with TRM1A and B, highlighting a new potential role between these enzymes. Work with At PRORPs led to the development of a ribonuclease that is being used to protect against plant viruses. The mitochondrial RNase P complex, found in metazoans, consists of PRORP, TRMT10C, and SDR5C1, and has also been shown to have substrate specificity, although the cause is unknown. Mutations in mitochondrial tRNA and mitochondrial RNase P have been linked to human disease, highlighting the need to continue understanding this complex. The last class of PRORPs, homologs of Aquifex RNase P (HARPs), is found in thermophilic archaea and bacteria. This most recently discovered type of PRORP forms a large homo-oligomer complex. Although numerous structures of HARPs have been published, it is still unclear how HARPs bind pre-tRNAs and in what ratio. There is also little investigation into the substrate specificity and ideal conditions for HARPs. Moving forward, further work is required to fully characterize each of the three classes of PRORP, the pre-tRNA binding recognition mechanism, the rules of substrate specificity, and how these three distinct classes of PRORP evolved. This article is categorized under: RNA Structure and Dynamics > RNA Structure, Dynamics and Chemistry RNA Structure and Dynamics > Influence of RNA Structure in Biological Systems.
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Affiliation(s)
| | - Kipchumba Kaitany
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
- Program in Biophysics, University of Michigan, Ann Arbor, Michigan, USA
| | - Abigail Kelly
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Matthew Yacoub
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Markos Koutmos
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
- Program in Biophysics, University of Michigan, Ann Arbor, Michigan, USA
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3
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Anders AG, Tidwell ED, Gadkari VV, Koutmos M, Ruotolo BT. Collision-Induced Unfolding Reveals Disease-Associated Stability Shifts in Mitochondrial Transfer Ribonucleic Acids. J Am Chem Soc 2024; 146:4412-4420. [PMID: 38329282 DOI: 10.1021/jacs.3c09230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Ribonucleic acids (RNAs) remain challenging targets for structural biology, creating barriers to understanding their vast functions in cellular biology and fully realizing their applications in biotechnology. The inherent dynamism of RNAs creates numerous obstacles in capturing their biologically relevant higher-order structures (HOSs), and as a result, many RNA functions remain unknown. In this study, we describe the development of native ion mobility-mass spectrometry and collision-induced unfolding (CIU) for the structural characterization of a variety of RNAs. We evaluate the ability of these techniques to preserve native structural features in the gas phase across a wide range of functional RNAs. Finally, we apply these tools to study the elusive mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes-associated A3243G mutation. Our data demonstrate that our experimentally determined conditions preserve some solution-state memory of RNAs via the correlated complexity of CIU fingerprints and RNA HOS, the observation of predicted stability shifts in the control RNA samples, and the retention of predicted magnesium binding events in gas-phase RNA ions. Significant differences in collision cross section and stability are observed as a function of the A3243G mutation across a subset of the mitochondrial tRNA maturation pathway. We conclude by discussing the potential application of CIU for the development of RNA-based biotherapeutics and, more broadly, transcriptomic characterization.
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Affiliation(s)
- Anna G Anders
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Elizabeth D Tidwell
- Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Varun V Gadkari
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Markos Koutmos
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Brandon T Ruotolo
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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Tidwell ED, Kilde IR, Leskaj S, Koutmos M. Fluorescent Ligand Equilibrium Displacement: A High-Throughput Method for Identification of FMN Riboswitch-Binding Small Molecules. Int J Mol Sci 2024; 25:735. [PMID: 38255809 DOI: 10.3390/ijms25020735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 12/27/2023] [Accepted: 12/28/2023] [Indexed: 01/24/2024] Open
Abstract
Antibiotic resistance remains a pressing global concern, with most antibiotics targeting the bacterial ribosome or a limited range of proteins. One class of underexplored antibiotic targets is bacterial riboswitches, structured RNA elements that regulate key biosynthetic pathways by binding a specific ligand. We developed a methodology termed Fluorescent Ligand Equilibrium Displacement (FLED) to rapidly discover small molecules that bind the flavin mononucleotide (FMN) riboswitch. FLED leverages intrinsically fluorescent FMN and the quenching effect on RNA binding to create a label-free, in vitro method to identify compounds that can bind the apo population of riboswitch in a system at equilibrium. The response difference between known riboswitch ligands and controls demonstrates the robustness of the method for high-throughput screening. An existing drug discovery library that was screened using FLED resulted in a final hit rate of 0.67%. The concentration response of each hit was determined and revealed a variety of approximate effective concentration values. Our preliminary screening data support the use of FLED to identify small molecules for medicinal chemistry development as FMN riboswitch-targeted antibiotic compounds. This robust, label-free, and cell-free method offers a strong alternative to other riboswitch screening methods and can be adapted to a variety of laboratory setups.
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Affiliation(s)
| | - Ingrid R Kilde
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Suada Leskaj
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Markos Koutmos
- Program in Biophysics, University of Michigan, Ann Arbor, MI 48109, USA
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
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5
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DeAngelo SL, Győrffy B, Koutmos M, Shah YM. Selenoproteins and tRNA-Sec: regulators of cancer redox homeostasis. Trends Cancer 2023; 9:1006-1018. [PMID: 37716885 PMCID: PMC10843386 DOI: 10.1016/j.trecan.2023.08.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 08/01/2023] [Accepted: 08/08/2023] [Indexed: 09/18/2023]
Abstract
In the past two decades significant progress has been made in uncovering the biological function of selenium. Selenium, an essential trace element, is required for the biogenesis of selenocysteine which is then incorporated into selenoproteins. These selenoproteins have emerged as central regulators of cellular antioxidant capacity and maintenance of redox homeostasis. This review provides a comprehensive examination of the multifaceted functions of selenoproteins with a particular emphasis on their contributions to cellular antioxidant capacity. Additionally, we highlight the promising potential of targeting selenoproteins and the biogenesis of selenocysteine as avenues for therapeutic intervention in cancer. By understanding the intricate relationship between selenium, selenoproteins, and reactive oxygen species (ROS), insights can be gained to develop therapies that exploit the inherent vulnerabilities of cancer cells.
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Affiliation(s)
- Stephen L DeAngelo
- Department of Cancer Biology, University of Michigan, Ann Arbor, MI, USA
| | - Balázs Győrffy
- Department of Bioinformatics, Semmelweis University, Budapest, Hungary
| | - Markos Koutmos
- Department of Cancer Biology, University of Michigan, Ann Arbor, MI, USA; Department of Chemistry, University of Michigan, Ann Arbor, MI, USA; Program in Biophysics, University of Michigan, Ann Arbor, MI, USA
| | - Yatrik M Shah
- Department of Cancer Biology, University of Michigan, Ann Arbor, MI, USA; Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA; Rogel Cancer Center, University of Michigan, Ann Arbor, MI, USA; Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA.
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6
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Wilhelm CA, Mallik L, Kelly AL, Brotzman S, Mendoza J, Anders AG, Leskaj S, Castillo C, Ruotolo BT, Cianfrocco MA, Koutmos M. Bacterial RNA-free RNase P: Structural and functional characterization of multiple oligomeric forms of a minimal protein-only ribonuclease P. J Biol Chem 2023; 299:105327. [PMID: 37806495 PMCID: PMC10652100 DOI: 10.1016/j.jbc.2023.105327] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 09/08/2023] [Accepted: 09/19/2023] [Indexed: 10/10/2023] Open
Abstract
tRNAs are typically transcribed with extended 5' and 3' ends that must be removed before they attain their active form. One of the first steps of tRNA processing in nearly every organism is the removal of the 5' leader sequence by ribonuclease P (RNase P). Here, we investigate a recently discovered class of RNase P enzymes, Homologs of Aquifex RNase P (HARPs). In contrast to other RNase Ps, HARPs consist only of a metallonuclease domain and lack the canonical substrate recognition domain essential in other classes of proteinaceous RNase P. We determined the cryo-EM structure of Aquifex aeolicus HARP (Aq880) and two crystal structures of Hydrogenobacter thermophilus HARP (Hth1307) to reveal that both enzymes form large ring-like assemblies: a dodecamer in Aq880 and a tetradecamer in Hth1307. In both oligomers, the enzyme active site is 42 Å away from a positively charged helical region, as seen in other protein-only RNase P enzymes, which likely serves to recognize and bind the elbow region of the pre-tRNA substrate. In addition, we use native mass spectrometry to confirm and characterize the previously unreported tetradecamer state. Notably, we find that multiple oligomeric states of Hth1307 are able to cleave pre-tRNAs. Furthermore, our single-turnover kinetic studies indicate that Hth1307 cleaves pre-tRNAs from multiple species with a preference for native substrates. These data provide a closer look at the nuanced similarities and differences in tRNA processing across disparate classes of RNase P.
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Affiliation(s)
| | - Leena Mallik
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA; Center for Computational and Genomic Medicine and Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Abigail L Kelly
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Shayna Brotzman
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Johnny Mendoza
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Anna G Anders
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Suada Leskaj
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Carmen Castillo
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Brandon T Ruotolo
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Michael A Cianfrocco
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, USA; Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, USA
| | - Markos Koutmos
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA; Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, USA; Program in Biophysics, University of Michigan, Ann Arbor, Michigan, USA.
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7
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Mendoza J, Purchal M, Yamada K, Koutmos M. Structure of full-length cobalamin-dependent methionine synthase and cofactor loading captured in crystallo. Nat Commun 2023; 14:6365. [PMID: 37821448 PMCID: PMC10567725 DOI: 10.1038/s41467-023-42037-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 09/28/2023] [Indexed: 10/13/2023] Open
Abstract
Cobalamin-dependent methionine synthase (MS) is a key enzyme in methionine and folate one-carbon metabolism. MS is a large multi-domain protein capable of binding and activating three substrates: homocysteine, folate, and S-adenosylmethionine for methylation. Achieving three chemically distinct methylations necessitates significant domain rearrangements to facilitate substrate access to the cobalamin cofactor at the right time. The distinct conformations required for each reaction have eluded structural characterization as its inherently dynamic nature renders structural studies difficult. Here, we use a thermophilic MS homolog (tMS) as a functional MS model. Its exceptional stability enabled characterization of MS in the absence of cobalamin, marking the only studies of a cobalamin-binding protein in its apoenzyme state. More importantly, we report the high-resolution full-length MS structure, ending a multi-decade quest. We also capture cobalamin loading in crystallo, providing structural insights into holoenzyme formation. Our work paves the way for unraveling how MS orchestrates large-scale domain rearrangements crucial for achieving challenging chemistries.
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Affiliation(s)
- Johnny Mendoza
- Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Meredith Purchal
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI, 48109, USA
- New England Biolabs, Inc., Ipswich, MA, 01938, England
| | - Kazuhiro Yamada
- Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA.
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA.
| | - Markos Koutmos
- Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA.
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI, 48109, USA.
- Program in Biophysics, University of Michigan, Ann Arbor, MI, 48109, USA.
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8
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Yamada K, Mendoza J, Koutmos M. 5-Formyltetrahydrofolate promotes conformational remodeling in a methylenetetrahydrofolate reductase active site and inhibits its activity. J Biol Chem 2023; 299:102855. [PMID: 36592927 PMCID: PMC9900621 DOI: 10.1016/j.jbc.2022.102855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 12/24/2022] [Accepted: 12/27/2022] [Indexed: 01/01/2023] Open
Abstract
The flavoprotein methylenetetrahydrofolate reductase (MTHFR) catalyzes the reduction of N5, N10-methylenetetrahydrofolate (CH2-H4folate) to N5-methyltetrahydrofolate (CH3-H4folate), committing a methyl group from the folate cycle to the methionine one. This committed step is the sum of multiple ping-pong electron transfers involving multiple substrates, intermediates, and products all sharing the same active site. Insight into folate substrate binding is needed to better understand this multifunctional active site. Here, we performed activity assays with Thermus thermophilus MTHFR (tMTHFR), which showed pH-dependent inhibition by the substrate analog, N5-formyltetrahydrofolate (CHO-H4folate). Our crystal structure of a tMTHFR•CHO-H4folate complex revealed a unique folate-binding mode; tMTHFR subtly rearranges its active site to form a distinct folate-binding environment. Formation of a novel binding pocket for the CHO-H4folate p-aminobenzoic acid moiety directly affects how bent the folate ligand is and its accommodation in the active site. Comparative analysis of the available active (FAD- and folate-bound) MTHFR complex structures reveals that CHO-H4folate is accommodated in the active site in a conformation that would not support hydride transfer, but rather in a conformation that potentially reports on a different step in the reaction mechanism after this committed step, such as CH2-H4folate ring-opening. This active site remodeling provides insights into the functional relevance of the differential folate-binding modes and their potential roles in the catalytic cycle. The conformational flexibility displayed by tMTHFR demonstrates how a shared active site can use a few amino acid residues in lieu of extra domains to accommodate chemically distinct moieties and functionalities.
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Affiliation(s)
- Kazuhiro Yamada
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA; Program in Biophysics, University of Michigan, Ann Arbor, Michigan, USA.
| | - Johnny Mendoza
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Markos Koutmos
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA; Program in Biophysics, University of Michigan, Ann Arbor, Michigan, USA; Program in Chemical Biology, University of Michigan, Ann Arbor, Michigan, USA.
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Wu Meyers N, Karasik A, Kaitany K, Fierke CA, Koutmos M. Gambogic acid and juglone inhibit RNase P through distinct mechanisms. J Biol Chem 2022; 298:102683. [PMID: 36370850 PMCID: PMC9731865 DOI: 10.1016/j.jbc.2022.102683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 11/02/2022] [Accepted: 11/05/2022] [Indexed: 11/11/2022] Open
Abstract
The first step in transfer RNA (tRNA) maturation is the cleavage of the 5' end of precursor tRNA (pre-tRNA) catalyzed by ribonuclease P (RNase P). RNase P is either a ribonucleoprotein complex with a catalytic RNA subunit or a protein-only RNase P (PRORP). In most land plants, algae, and Euglenozoa, PRORP is a single-subunit enzyme. There are currently no inhibitors of PRORP for use as tools to study the biological function of this enzyme. Therefore, we screened for compounds that inhibit the activity of a model PRORP from A. thaliana organelles (PRORP1) using a high throughput fluorescence polarization cleavage assay. Two compounds, gambogic acid and juglone (5-hydroxy-1,4-naphthalenedione) that inhibit PRORP1 in the 1 μM range were identified and analyzed. We found these compounds similarly inhibit human mtRNase P, a multisubunit protein enzyme and are 50-fold less potent against bacterial RNA-dependent RNase P. Our biochemical measurements indicate that gambogic acid is a rapid-binding, uncompetitive inhibitor targeting the PRORP1-substrate complex, while juglone acts as a time-dependent PRORP1 inhibitor. Additionally, X-ray crystal structures of PRORP1 in complex with juglone demonstrate the formation of a covalent complex with cysteine side chains on the surface of the protein. Finally, we propose a model consistent with the kinetic data that involves juglone binding to PRORP1 rapidly to form an inactive enzyme-inhibitor complex and then undergoing a slow step to form an inactive covalent adduct with PRORP1. These inhibitors have the potential to be developed into tools to probe PRORP structure and function relationships.
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Affiliation(s)
- Nancy Wu Meyers
- Program in Chemical Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Agnes Karasik
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Kipchumba Kaitany
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Carol A. Fierke
- Program in Chemical Biology, University of Michigan, Ann Arbor, Michigan, USA,Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA,For correspondence: Markos Koutmos; Carol A. Fierke
| | - Markos Koutmos
- Program in Chemical Biology, University of Michigan, Ann Arbor, Michigan, USA,Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA,Program in Biophysics, University of Michigan, Ann Arbor, Michigan, USA,For correspondence: Markos Koutmos; Carol A. Fierke
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10
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Ruetz M, Koutmos M, Kräutler B. Antivitamins B 12: Synthesis and application as inhibitory ligand of the B 12-tailoring enzyme CblC. Methods Enzymol 2022; 668:157-178. [PMID: 35589193 DOI: 10.1016/bs.mie.2021.12.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Antivitamins B12 are non-natural corrinoids that have been designed to counteract the metabolic effects of vitamin B12 and related cobalamins (Cbls) in humans and other mammals. A basic structure- and reactivity-based concept typifies antivitamins B12 as close structural mimics of vitamin B12 that are not transformed by the cellular metabolism into organometallic B12-cofactors. Antivitamins B12 have the correct structure for efficient take-up and transport via the natural mammalian pathway for cobalamin assimilation. Thus they can be delivered to every cell in the body, where they are proposed to target and inhibit the Cbl tailoring enzyme CblC. Antivitamins B12 may be specifically inert Cbls or isostructural Cbl-analogues that carry a metal centre other than a cobalt-ion. The syntheses of two antivitamins B12 are detailed here, as are biochemical and crystallographic studies that provide insights into the crucial binding interactions of Cbl-based antivitamins B12 with the human B12-tailoring enzyme CblC. This key enzyme binds genuine antivitamins B12 as inert substrate mimics and enzyme inhibitors, effectively repressing the metabolic generation of the B12-cofactors. Hence, antivitamins B12 induce the diagnostic symptoms of (functional) B12-deficiency, as observed in healthy laboratory mice.
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Affiliation(s)
- Markus Ruetz
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Markos Koutmos
- Department of Chemistry, Program in Biophysics, Program in Chemical Biology, University of Michigan, Ann Arbor, MI, United States.
| | - Bernhard Kräutler
- Institute of Organic Chemistry and Center of Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
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11
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Purchal MK, Eyler DE, Tardu M, Franco MK, Korn MM, Khan T, McNassor R, Giles R, Lev K, Sharma H, Monroe J, Mallik L, Koutmos M, Koutmou KS. Pseudouridine synthase 7 is an opportunistic enzyme that binds and modifies substrates with diverse sequences and structures. Proc Natl Acad Sci U S A 2022; 119:e2109708119. [PMID: 35058356 PMCID: PMC8794802 DOI: 10.1073/pnas.2109708119] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 11/17/2021] [Indexed: 12/13/2022] Open
Abstract
Pseudouridine (Ψ) is a ubiquitous RNA modification incorporated by pseudouridine synthase (Pus) enzymes into hundreds of noncoding and protein-coding RNA substrates. Here, we determined the contributions of substrate structure and protein sequence to binding and catalysis by pseudouridine synthase 7 (Pus7), one of the principal messenger RNA (mRNA) modifying enzymes. Pus7 is distinct among the eukaryotic Pus proteins because it modifies a wider variety of substrates and shares limited homology with other Pus family members. We solved the crystal structure of Saccharomyces cerevisiae Pus7, detailing the architecture of the eukaryotic-specific insertions thought to be responsible for the expanded substrate scope of Pus7. Additionally, we identified an insertion domain in the protein that fine-tunes Pus7 activity both in vitro and in cells. These data demonstrate that Pus7 preferentially binds substrates possessing the previously identified UGUAR (R = purine) consensus sequence and that RNA secondary structure is not a strong requirement for Pus7-binding. In contrast, the rate constants and extent of Ψ incorporation are more influenced by RNA structure, with Pus7 modifying UGUAR sequences in less-structured contexts more efficiently both in vitro and in cells. Although less-structured substrates were preferred, Pus7 fully modified every transfer RNA, mRNA, and nonnatural RNA containing the consensus recognition sequence that we tested. Our findings suggest that Pus7 is a promiscuous enzyme and lead us to propose that factors beyond inherent enzyme properties (e.g., enzyme localization, RNA structure, and competition with other RNA-binding proteins) largely dictate Pus7 substrate selection.
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Affiliation(s)
- Meredith K Purchal
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109
| | - Daniel E Eyler
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
| | - Mehmet Tardu
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
| | - Monika K Franco
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109
| | - Megan M Korn
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
| | - Taslima Khan
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109
| | - Ryan McNassor
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
| | - Rachel Giles
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
| | - Katherine Lev
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109
| | - Hari Sharma
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
| | - Jeremy Monroe
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
| | - Leena Mallik
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109
| | - Markos Koutmos
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109;
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109
| | - Kristin S Koutmou
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109;
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
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12
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Gouda H, Mascarenhas R, Pillay S, Ruetz M, Koutmos M, Banerjee R. Patient mutations in human ATP:cob(I)alamin adenosyltransferase differentially affect its catalytic versus chaperone functions. J Biol Chem 2021; 297:101373. [PMID: 34757128 PMCID: PMC8633584 DOI: 10.1016/j.jbc.2021.101373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 10/25/2021] [Accepted: 10/27/2021] [Indexed: 11/26/2022] Open
Abstract
Human ATP:cob(I)alamin adenosyltransferase (ATR) is a mitochondrial enzyme that catalyzes an adenosyl transfer to cob(I)alamin, synthesizing 5′-deoxyadenosylcobalamin (AdoCbl) or coenzyme B12. ATR is also a chaperone that escorts AdoCbl, transferring it to methylmalonyl-CoA mutase, which is important in propionate metabolism. Mutations in ATR lead to methylmalonic aciduria type B, an inborn error of B12 metabolism. Our previous studies have furnished insights into how ATR protein dynamics influence redox-linked cobalt coordination chemistry, controlling its catalytic versus chaperone functions. In this study, we have characterized three patient mutations at two conserved active site residues in human ATR, R190C/H, and E193K and obtained crystal structures of R190C and E193K variants, which display only subtle structural changes. All three mutations were found to weaken affinities for the cob(II)alamin substrate and the AdoCbl product and increase KM(ATP). 31P NMR studies show that binding of the triphosphate product, formed during the adenosylation reaction, is also weakened. However, although the kcat of this reaction is significantly diminished for the R190C/H mutants, it is comparable with the WT enzyme for the E193K variant, revealing the catalytic importance of Arg-190. Furthermore, although the E193K mutation selectively impairs the chaperone function by promoting product release into solution, its catalytic function might be unaffected at physiological ATP concentrations. In contrast, the R190C/H mutations affect both the catalytic and chaperoning activities of ATR. Because the E193K mutation spares the catalytic activity of ATR, our data suggest that the patients carrying this mutation are more likely to be responsive to cobalamin therapy.
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Affiliation(s)
- Harsha Gouda
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Romila Mascarenhas
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Shubhadra Pillay
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Markus Ruetz
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Markos Koutmos
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA; Department of Biophysics, University of Michigan, Ann Arbor, Michigan, USA
| | - Ruma Banerjee
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, USA.
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13
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Karasik A, Wilhelm CA, Fierke CA, Koutmos M. Disease-associated mutations in mitochondrial precursor tRNAs affect binding, m1R9 methylation, and tRNA processing by mtRNase P. RNA 2021; 27:420-432. [PMID: 33380464 PMCID: PMC7962481 DOI: 10.1261/rna.077198.120] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 12/16/2020] [Indexed: 06/12/2023]
Abstract
Mitochondrial diseases linked to mutations in mitochondrial (mt) tRNA sequences are common. However, the contributions of these tRNA mutations to the development of diseases is mostly unknown. Mutations may affect interactions with (mt)tRNA maturation enzymes or protein synthesis machinery leading to mitochondrial dysfunction. In human mitochondria, in most cases the first step of tRNA processing is the removal of the 5' leader of precursor tRNAs (pre-tRNA) catalyzed by the three-component enzyme, mtRNase P. Additionally, one component of mtRNase P, mitochondrial RNase P protein 1 (MRPP1), catalyzes methylation of the R9 base in pre-tRNAs. Despite the central role of 5' end processing in mitochondrial tRNA maturation, the link between mtRNase P and diseases is mostly unexplored. Here, we investigate how 11 different human disease-linked mutations in (mt)pre-tRNAIle, (mt)pre-tRNALeu(UUR), and (mt)pre-tRNAMet affect the activities of mtRNase P. We find that several mutations weaken the pre-tRNA binding affinity (KD s are approximately two- to sixfold higher than that of wild-type), while the majority of mutations decrease 5' end processing and methylation activity catalyzed by mtRNase P (up to ∼55% and 90% reduction, respectively). Furthermore, all of the investigated mutations in (mt)pre-tRNALeu(UUR) alter the tRNA fold which contributes to the partial loss of function of mtRNase P. Overall, these results reveal an etiological link between early steps of (mt)tRNA-substrate processing and mitochondrial disease.
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Affiliation(s)
- Agnes Karasik
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
| | - Catherine A Wilhelm
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Carol A Fierke
- Department of Chemistry, Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
- Department of Chemistry, Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
| | - Markos Koutmos
- Department of Chemistry, Program in Biophysics, University of Michigan, Ann Arbor, Michigan 48109, USA
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14
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Miller NA, Kaneshiro AK, Konar A, Alonso-Mori R, Britz A, Deb A, Glownia JM, Koralek JD, Mallik L, Meadows JH, Michocki LB, van Driel TB, Koutmos M, Padmanabhan S, Elías-Arnanz M, Kubarych KJ, Marsh ENG, Penner-Hahn JE, Sension RJ. The Photoactive Excited State of the B 12-Based Photoreceptor CarH. J Phys Chem B 2020; 124:10732-10738. [PMID: 33174757 DOI: 10.1021/acs.jpcb.0c09428] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have used transient absorption spectroscopy in the UV-visible and X-ray regions to characterize the excited state of CarH, a protein photoreceptor that uses a form of B12, adenosylcobalamin (AdoCbl), to sense light. With visible excitation, a nanosecond-lifetime photoactive excited state is formed with unit quantum yield. The time-resolved X-ray absorption near edge structure difference spectrum of this state demonstrates that the excited state of AdoCbl in CarH undergoes only modest structural expansion around the central cobalt, a behavior similar to that observed for methylcobalamin rather than for AdoCbl free in solution. We propose a new mechanism for CarH photoreactivity involving formation of a triplet excited state. This allows the sensor to operate with high quantum efficiency and without formation of potentially dangerous side products. By stabilizing the excited electronic state, CarH controls reactivity of AdoCbl and enables slow reactions that yield nonreactive products and bypass bond homolysis and reactive radical species formation.
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Affiliation(s)
- Nicholas A Miller
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - April K Kaneshiro
- Department of Biological Chemistry, University of Michigan, 1150 W. Medical Center Dr., Ann Arbor, Michigan 48109-0600, United States
| | - Arkaprabha Konar
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
| | - Roberto Alonso-Mori
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Alexander Britz
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States.,Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Aniruddha Deb
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States.,Department of Biophysics, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - James M Glownia
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Jake D Koralek
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Leena Mallik
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Joseph H Meadows
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Lindsay B Michocki
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Tim B van Driel
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Markos Koutmos
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States.,Department of Biophysics, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - S Padmanabhan
- Instituto de Química Física "Rocasolano", Consejo Superior de Investigaciones Científicas, Madrid 28006, Spain
| | - Montserrat Elías-Arnanz
- Departamento de Genética y Microbiología, Área de Genética (Unidad Asociada al Instituto de Química Física "Rocasolano", Consejo Superior de Investigaciones Científicas), Facultad de Biología, Universidad de Murcia, Murcia 30100, Spain
| | - Kevin J Kubarych
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - E Neil G Marsh
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - James E Penner-Hahn
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States.,Department of Biophysics, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Roseanne J Sension
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States.,Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States.,Department of Biophysics, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
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15
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Li Z, Mascarenhas R, Twahir UT, Kallon A, Deb A, Yaw M, Penner-Hahn J, Koutmos M, Warncke K, Banerjee R. An Interprotein Co-S Coordination Complex in the B 12-Trafficking Pathway. J Am Chem Soc 2020; 142:16334-16345. [PMID: 32871076 DOI: 10.1021/jacs.0c06590] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The CblC and CblD chaperones are involved in early steps in the cobalamin trafficking pathway. Cobalamin derivatives entering the cytoplasm are converted by CblC to a common cob(II)alamin intermediate via glutathione-dependent alkyltransferase or reductive elimination activities. Cob(II)alamin is subsequently converted to one of two biologically active alkylcobalamins by downstream chaperones. The function of CblD has been elusive although it is known to form a complex with CblC under certain conditions. Here, we report that CblD provides a sulfur ligand to cob(II)alamin bound to CblC, forming an interprotein coordination complex that rapidly oxidizes to thiolato-cob(III)alamin. Cysteine scanning mutagenesis and EPR spectroscopy identified Cys-261 on CblD as the sulfur donor. The unusual interprotein Co-S bond was characterized by X-ray absorption spectroscopy and visualized in the crystal structure of the human CblD thiolato-cob(III)alamin complex. Our study provides insights into how cobalamin coordination chemistry could be utilized for cofactor translocation in the trafficking pathway.
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Affiliation(s)
- Zhu Li
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600, United States
| | - Romila Mascarenhas
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600, United States
| | - Umar T Twahir
- Department of Physics, Emory University, Atlanta, Georgia 30322-2430, United States
| | - Albert Kallon
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600, United States
| | - Aniruddha Deb
- Departments of Chemistry and Biophysics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Madeline Yaw
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600, United States
| | - James Penner-Hahn
- Departments of Chemistry and Biophysics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Markos Koutmos
- Departments of Chemistry and Biophysics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Kurt Warncke
- Department of Physics, Emory University, Atlanta, Georgia 30322-2430, United States
| | - Ruma Banerjee
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600, United States
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16
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Lukowski AL, Mallik L, Hinze ME, Carlson BM, Ellinwood DC, Pyser JB, Koutmos M, Narayan ARH. Substrate Promiscuity of a Paralytic Shellfish Toxin Amidinotransferase. ACS Chem Biol 2020; 15:626-631. [PMID: 32058687 DOI: 10.1021/acschembio.9b00964] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Secondary metabolites are assembled by enzymes that often perform reactions with high selectivity and specificity. Many of these enzymes also tolerate variations in substrate structure, exhibiting promiscuity that enables various applications of a given biocatalyst. However, initial enzyme characterization studies frequently do not explore beyond the native substrates. This limited assessment of substrate scope contributes to the difficulty of identifying appropriate enzymes for specific synthetic applications. Here, we report the natural function of cyanobacterial SxtG, an amidinotransferase involved in the biosynthesis of paralytic shellfish toxins, and demonstrate its ability to modify a breadth of non-native substrates. In addition, we report the first X-ray crystal structure of SxtG, which provides rationale for this enzyme's substrate scope. Taken together, these data confirm the function of SxtG and exemplify its potential utility in biocatalytic synthesis.
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17
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Karasik A, Fierke CA, Koutmos M. Interplay between substrate recognition, 5' end tRNA processing and methylation activity of human mitochondrial RNase P. RNA 2019; 25:1646-1660. [PMID: 31455609 PMCID: PMC6859853 DOI: 10.1261/rna.069310.118] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 08/16/2019] [Indexed: 05/07/2023]
Abstract
Human mitochondrial ribonuclease P (mtRNase P) is an essential three-protein complex that catalyzes the 5' end maturation of mitochondrial precursor tRNAs (pre-tRNAs). Mitochondrial RNase P Protein 3 (MRPP3), a protein-only RNase P (PRORP), is the nuclease component of the mtRNase P complex and requires a two-protein S-adenosyl-methionine (SAM)-dependent methyltransferase MRPP1/2 subcomplex to function. Dysfunction of mtRNase P is linked to several human mitochondrial diseases, such as mitochondrial myopathies. Despite its central role in mitochondrial RNA processing, little is known about how the protein subunits of mtRNase P function synergistically. Here, we use purified mtRNase P to demonstrate that mtRNase P recognizes, cleaves, and methylates some, but not all, mitochondrial pre-tRNAs in vitro. Additionally, mtRNase P does not process all mitochondrial pre-tRNAs uniformly, suggesting the possibility that some pre-tRNAs require additional factors to be cleaved in vivo. Consistent with this, we found that addition of the TRMT10C (MRPP1) cofactor SAM enhances the ability of mtRNase P to bind and cleave some mitochondrial pre-tRNAs. Furthermore, the presence of MRPP3 can enhance the methylation activity of MRPP1/2. Taken together, our data demonstrate that the subunits of mtRNase P work together to efficiently recognize, process, and methylate human mitochondrial pre-tRNAs.
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Affiliation(s)
- Agnes Karasik
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
| | - Carol A Fierke
- Department of Chemistry, Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Markos Koutmos
- Department of Chemistry, Program in Biophysics, University of Michigan, Ann Arbor, Michigan 48109, USA
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18
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Ruetz M, Campanello GC, Purchal M, Shen H, McDevitt L, Gouda H, Wakabayashi S, Zhu J, Rubin EJ, Warncke K, Mootha VK, Koutmos M, Banerjee R. Itaconyl-CoA forms a stable biradical in methylmalonyl-CoA mutase and derails its activity and repair. Science 2019; 366:589-593. [PMID: 31672889 PMCID: PMC7070230 DOI: 10.1126/science.aay0934] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Accepted: 09/03/2019] [Indexed: 12/28/2022]
Abstract
Itaconate is an immunometabolite with both anti-inflammatory and bactericidal effects. Its coenzyme A (CoA) derivative, itaconyl-CoA, inhibits B12-dependent methylmalonyl-CoA mutase (MCM) by an unknown mechanism. We demonstrate that itaconyl-CoA is a suicide inactivator of human and Mycobacterium tuberculosis MCM, which forms a markedly air-stable biradical adduct with the 5'-deoxyadenosyl moiety of the B12 coenzyme. Termination of the catalytic cycle in this way impairs communication between MCM and its auxiliary repair proteins. Crystallography and spectroscopy of the inhibited enzyme are consistent with a metal-centered cobalt radical ~6 angstroms away from the tertiary carbon-centered radical and suggest a means of controlling radical trajectories during MCM catalysis. Mycobacterial MCM thus joins enzymes in the glyoxylate shunt and the methylcitrate cycle as targets of itaconate in pathogen propionate metabolism.
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Affiliation(s)
- Markus Ruetz
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Gregory C Campanello
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Meredith Purchal
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Hongying Shen
- Howard Hughes Medical Institute and Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Broad Institute, Cambridge, MA 02142, USA
| | - Liam McDevitt
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Harsha Gouda
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Shoko Wakabayashi
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Cambridge, MA 02115, USA
| | - Junhao Zhu
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Cambridge, MA 02115, USA
| | - Eric J Rubin
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Cambridge, MA 02115, USA
| | - Kurt Warncke
- Department of Physics, Emory University, Atlanta, GA 30322, USA
| | - Vamsi K Mootha
- Howard Hughes Medical Institute and Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Broad Institute, Cambridge, MA 02142, USA
| | - Markos Koutmos
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
- Program in Biophysics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Ruma Banerjee
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
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19
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Yamada K, Koutmos M. The folate-binding module of Thermus thermophilus cobalamin-dependent methionine synthase displays a distinct variation of the classical TIM barrel: a TIM barrel with a `twist'. Acta Crystallogr D Struct Biol 2018; 74:41-51. [PMID: 29372898 DOI: 10.1107/s2059798317018290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 12/21/2017] [Indexed: 11/10/2022]
Abstract
Methyl transfer between methyltetrahydrofolate and corrinoid molecules is a key reaction in biology that is catalyzed by a number of enzymes in many prokaryotic and eukaryotic organisms. One classic example of such an enzyme is cobalamin-dependent methionine synthase (MS). MS is a large modular protein that utilizes an SN2-type mechanism to catalyze the chemically challenging methyl transfer from the tertiary amine (N5) of methyltetrahydrofolate to homocysteine in order to form methionine. Despite over half a century of study, many questions remain about how folate-dependent methyltransferases, and MS in particular, function. Here, the structure of the folate-binding (Fol) domain of MS from Thermus thermophilus is reported in the presence and absence of methyltetrahydrofolate. It is found that the methyltetrahydrofolate-binding environment is similar to those of previously described methyltransferases, highlighting the conserved role of this domain in binding, and perhaps activating, the methyltetrahydrofolate substrate. These structural studies further reveal a new distinct and uncharacterized topology in the C-terminal region of MS Fol domains. Furthermore, it is found that in contrast to the canonical TIM-barrel β8α8 fold found in all other folate-binding domains, MS Fol domains exhibit a unique β8α7 fold. It is posited that these structural differences are important for MS function.
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Affiliation(s)
- Kazuhiro Yamada
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Markos Koutmos
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
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20
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Klemm BP, Karasik A, Kaitany KJ, Shanmuganathan A, Henley MJ, Thelen AZ, Dewar AJL, Jackson ND, Koutmos M, Fierke CA. Molecular recognition of pre-tRNA by Arabidopsis protein-only Ribonuclease P. RNA 2017; 23:1860-1873. [PMID: 28874505 PMCID: PMC5689006 DOI: 10.1261/rna.061457.117] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 08/31/2017] [Indexed: 05/06/2023]
Abstract
Protein-only ribonuclease P (PRORP) is an enzyme responsible for catalyzing the 5' end maturation of precursor transfer ribonucleic acids (pre-tRNAs) encoded by various cellular compartments in many eukaryotes. PRORPs from plants act as single-subunit enzymes and have been used as a model system for analyzing the function of the metazoan PRORP nuclease subunit, which requires two additional proteins for efficient catalysis. There are currently few molecular details known about the PRORP-pre-tRNA complex. Here, we characterize the determinants of substrate recognition by the single subunit Arabidopsis thaliana PRORP1 and PRORP2 using kinetic and thermodynamic experiments. The salt dependence of binding affinity suggests 4-5 contacts with backbone phosphodiester bonds on substrates, including a single phosphodiester contact with the pre-tRNA 5' leader, consistent with prior reports of short leader requirements. PRORPs contain an N-terminal pentatricopeptide repeat (PPR) domain, truncation of which results in a >30-fold decrease in substrate affinity. While most PPR-containing proteins have been implicated in single-stranded sequence-specific RNA recognition, we find that the PPR motifs of PRORPs recognize pre-tRNA substrates differently. Notably, the PPR domain residues most important for substrate binding in PRORPs do not correspond to positions involved in base recognition in other PPR proteins. Several of these residues are highly conserved in PRORPs from algae, plants, and metazoans, suggesting a conserved strategy for substrate recognition by the PRORP PPR domain. Furthermore, there is no evidence for sequence-specific interactions. This work clarifies molecular determinants of PRORP-substrate recognition and provides a new predictive model for the PRORP-substrate complex.
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Affiliation(s)
- Bradley P Klemm
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Agnes Karasik
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
| | - Kipchumba J Kaitany
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Aranganathan Shanmuganathan
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
| | - Matthew J Henley
- Program in Chemical Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Adam Z Thelen
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Allison J L Dewar
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Nathaniel D Jackson
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
| | - Markos Koutmos
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
| | - Carol A Fierke
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
- Program in Chemical Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
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21
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Ruetz M, Shanmuganathan A, Gherasim C, Karasik A, Salchner R, Kieninger C, Wurst K, Banerjee R, Koutmos M, Kräutler B. Inhibierung des humanen B12-verarbeitenden Enzyms CblC durch Antivitamine B12- Kristallstruktur des inaktiven ternären Komplexes mit dem Kosubstrat Glutathion. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201701583] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Markus Ruetz
- Institut für Organische Chemie und Zentrum für Molekulare, Biowissenschaften; Universität Innsbruck; 6020 Innsbruck Österreich
- University of Michigan Medical School; Ann Arbor MI 48109-0600 USA
| | | | - Carmen Gherasim
- University of Michigan Medical School; Ann Arbor MI 48109-0600 USA
- Department of Pathology; University of Utah School of Medicine; Salt Lake City UT USA
| | - Agnes Karasik
- Department of Biochemistry; Uniformed Services University of the Health Sciences; Bethesda MD 28104 USA
| | - Robert Salchner
- Institut für Organische Chemie und Zentrum für Molekulare, Biowissenschaften; Universität Innsbruck; 6020 Innsbruck Österreich
- Watercryst GmbH & Co; Kematen Österreich
| | - Christoph Kieninger
- Institut für Organische Chemie und Zentrum für Molekulare, Biowissenschaften; Universität Innsbruck; 6020 Innsbruck Österreich
| | - Klaus Wurst
- Institut für Allgemeine, Anorganische Chemie und Theoretische Chemie; Universität Innsbruck; Österreich
| | - Ruma Banerjee
- University of Michigan Medical School; Ann Arbor MI 48109-0600 USA
| | - Markos Koutmos
- Department of Biochemistry; Uniformed Services University of the Health Sciences; Bethesda MD 28104 USA
| | - Bernhard Kräutler
- Institut für Organische Chemie und Zentrum für Molekulare, Biowissenschaften; Universität Innsbruck; 6020 Innsbruck Österreich
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22
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Ruetz M, Shanmuganathan A, Gherasim C, Karasik A, Salchner R, Kieninger C, Wurst K, Banerjee R, Koutmos M, Kräutler B. Antivitamin B 12 Inhibition of the Human B 12 -Processing Enzyme CblC: Crystal Structure of an Inactive Ternary Complex with Glutathione as the Cosubstrate. Angew Chem Int Ed Engl 2017; 56:7387-7392. [PMID: 28544088 DOI: 10.1002/anie.201701583] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Indexed: 02/06/2023]
Abstract
B12 antivitamins are important and robust tools for investigating the biological roles of vitamin B12 . Here, the potential antivitamin B12 2,4-difluorophenylethynylcobalamin (F2PhEtyCbl) was prepared, and its 3D structure was studied in solution and in the crystal. Chemically inert F2PhEtyCbl resisted thermolysis of its Co-C bond at 100 °C, was stable in bright daylight, and also remained intact upon prolonged storage in aqueous solution at room temperature. It binds to the human B12 -processing enzyme CblC with high affinity (KD =130 nm) in the presence of the cosubstrate glutathione (GSH). F2PhEtyCbl withstood tailoring by CblC, and it also stabilized the ternary complex with GSH. The crystal structure of this inactivated assembly provides first insight into the binding interactions between an antivitamin B12 and CblC, as well as into the organization of GSH and a base-off cobalamin in the active site of this enzyme.
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Affiliation(s)
- Markus Ruetz
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, 6020, Innsbruck, Austria.,University of Michigan Medical School, Ann Arbor, USA
| | | | - Carmen Gherasim
- University of Michigan Medical School, Ann Arbor, USA.,Current address: Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Agnes Karasik
- Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, USA
| | - Robert Salchner
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, 6020, Innsbruck, Austria.,Current address: Watercryst GmbH & Co, Kematen, Austria
| | - Christoph Kieninger
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, 6020, Innsbruck, Austria
| | - Klaus Wurst
- Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Austria
| | - Ruma Banerjee
- University of Michigan Medical School, Ann Arbor, USA
| | - Markos Koutmos
- Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, USA
| | - Bernhard Kräutler
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, 6020, Innsbruck, Austria
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23
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Li Z, Shanmuganathan A, Ruetz M, Yamada K, Lesniak NA, Kräutler B, Brunold TC, Koutmos M, Banerjee R. Coordination chemistry controls the thiol oxidase activity of the B 12-trafficking protein CblC. J Biol Chem 2017; 292:9733-9744. [PMID: 28442570 DOI: 10.1074/jbc.m117.788554] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 04/20/2017] [Indexed: 01/20/2023] Open
Abstract
The cobalamin or B12 cofactor supports sulfur and one-carbon metabolism and the catabolism of odd-chain fatty acids, branched-chain amino acids, and cholesterol. CblC is a B12-processing enzyme involved in an early cytoplasmic step in the cofactor-trafficking pathway. It catalyzes the glutathione (GSH)-dependent dealkylation of alkylcobalamins and the reductive decyanation of cyanocobalamin. CblC from Caenorhabditis elegans (ceCblC) also exhibits a robust thiol oxidase activity, converting reduced GSH to oxidized GSSG with concomitant scrubbing of ambient dissolved O2 The mechanism of thiol oxidation catalyzed by ceCblC is not known. In this study, we demonstrate that novel coordination chemistry accessible to ceCblC-bound cobalamin supports its thiol oxidase activity via a glutathionyl-cobalamin intermediate. Deglutathionylation of glutathionyl-cobalamin by a second molecule of GSH yields GSSG. The crystal structure of ceCblC provides insights into how architectural differences at the α- and β-faces of cobalamin promote the thiol oxidase activity of ceCblC but mute it in wild-type human CblC. The R161G and R161Q mutations in human CblC unmask its latent thiol oxidase activity and are correlated with increased cellular oxidative stress disease. In summary, we have uncovered key architectural features in the cobalamin-binding pocket that support unusual cob(II)alamin coordination chemistry and enable the thiol oxidase activity of ceCblC.
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Affiliation(s)
- Zhu Li
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600
| | - Aranganathan Shanmuganathan
- the Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814
| | - Markus Ruetz
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600
| | - Kazuhiro Yamada
- the Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814
| | - Nicholas A Lesniak
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600
| | - Bernhard Kräutler
- the Institute of Organic Chemistry and Centre of Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria, and
| | - Thomas C Brunold
- the Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - Markos Koutmos
- the Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814
| | - Ruma Banerjee
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600,
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24
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Howard MJ, Karasik A, Klemm BP, Mei C, Shanmuganathan A, Fierke CA, Koutmos M. Differential substrate recognition by isozymes of plant protein-only Ribonuclease P. RNA 2016; 22:782-92. [PMID: 26966150 PMCID: PMC4836652 DOI: 10.1261/rna.055541.115] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Accepted: 02/10/2016] [Indexed: 05/22/2023]
Abstract
Ribonuclease P (RNase P) catalyzes the cleavage of leader sequences from precursor tRNA (pre-tRNA). Typically, these enzymes are ribonucleic protein complexes that are found in all domains of life. However, a new class of RNase P has been discovered that is composed entirely of protein, termed protein-only RNase P (PRORP). To investigate the molecular determinants of PRORP substrate recognition, we measured the binding affinities and cleavage kinetics of Arabidopsis PRORP1 for varied pre-tRNA substrates. This analysis revealed that PRORP1 does not make significant contacts within the trailer or beyond N-1of the leader, indicating that this enzyme recognizes primarily the tRNA body. To determine the extent to which sequence variation within the tRNA body modulates substrate selectivity and to provide insight into the evolution and function of PRORP enzymes, we measured the reactivity of the three Arabidopsis PRORP isozymes (PRORP1-3) with four pre-tRNA substrates. A 13-fold range in catalytic efficiencies (10(4)-10(5)M(-1)s(-1)) was observed, demonstrating moderate selectivity for pre-tRNA substrates. Although PRORPs bind the different pre-tRNA species with affinities varying by as much as 100-fold, the three isozymes have similar affinities for a given pre-tRNA, suggesting similar binding modes. However, PRORP isozymes have varying degrees of cleavage fidelity, which is dependent on the pre-tRNA species and the presence of a 3'-discriminator base. This work defines molecular determinants of PRORP substrate recognition that provides insight into this new class of RNA processing enzymes.
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Affiliation(s)
- Michael J Howard
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Agnes Karasik
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
| | - Bradley P Klemm
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Christine Mei
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Aranganathan Shanmuganathan
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
| | - Carol A Fierke
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Markos Koutmos
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
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25
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Sen A, Karasik A, Shanmuganathan A, Mirkovic E, Koutmos M, Cox RT. Loss of the mitochondrial protein-only ribonuclease P complex causes aberrant tRNA processing and lethality in Drosophila. Nucleic Acids Res 2016; 44:6409-22. [PMID: 27131785 PMCID: PMC5291253 DOI: 10.1093/nar/gkw338] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 04/14/2016] [Indexed: 12/26/2022] Open
Abstract
Proteins encoded by mitochondrial DNA are translated using mitochondrially encoded tRNAs and rRNAs. As with nuclear encoded tRNAs, mitochondrial tRNAs must be processed to become fully functional. The mitochondrial form of ribonuclease P (mt:RNase P) is responsible for 5′-end maturation and is comprised of three proteins; mitochondrial RNase P protein (MRPP) 1 and 2 together with proteinaceous RNase P (PRORP). However, its mechanism and impact on development is not yet known. Using homology searches, we have identified the three proteins composing Drosophila mt:RNase P: Mulder (PRORP), Scully (MRPP2) and Roswell (MRPP1). Here, we show that each protein is essential and localizes with mitochondria. Furthermore, reducing levels of each causes mitochondrial deficits, which appear to be due at least in part to defective mitochondrial tRNA processing. Overexpressing two members of the complex, Mulder and Roswell, is also lethal, and in the case of Mulder, causes abnormal mitochondrial morphology. These data are the first evidence that defective mt:RNase P causes mitochondrial dysfunction, lethality and aberrant mitochondrial tRNA processing in vivo, underscoring its physiological importance. This in vivo mt:RNase P model will advance our understanding of how loss of mitochondrial tRNA processing causes tissue failure, an important aspect of human mitochondrial disease.
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Affiliation(s)
- Aditya Sen
- Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, MD, 20814, USA
| | - Agnes Karasik
- Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, MD, 20814, USA
| | | | | | - Markos Koutmos
- Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, MD, 20814, USA
| | - Rachel T Cox
- Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, MD, 20814, USA
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26
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Yamada K, Gherasim C, Banerjee R, Koutmos M. Structure of Human B12 Trafficking Protein CblD Reveals Molecular Mimicry and Identifies a New Subfamily of Nitro-FMN Reductases. J Biol Chem 2015; 290:29155-66. [PMID: 26364851 PMCID: PMC4705922 DOI: 10.1074/jbc.m115.682435] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Indexed: 01/07/2023] Open
Abstract
In mammals, B12 (or cobalamin) is an essential cofactor required by methionine synthase and methylmalonyl-CoA mutase. A complex intracellular pathway supports the assimilation of cobalamin into its active cofactor forms and delivery to its target enzymes. MMADHC (the methylmalonic aciduria and homocystinuria type D protein), commonly referred to as CblD, is a key chaperone involved in intracellular cobalamin trafficking, and mutations in CblD cause methylmalonic aciduria and/or homocystinuria. Herein, we report the first crystal structure of the globular C-terminal domain of human CblD, which is sufficient for its interaction with MMADHC (the methylmalonic aciduria and homocystinuria type C protein), or CblC, and for supporting the cytoplasmic cobalamin trafficking pathway. CblD contains an α+β fold that is structurally reminiscent of the nitro-FMN reductase superfamily. Two of the closest structural relatives of CblD are CblC, a multifunctional enzyme important for cobalamin trafficking, and the activation domain of methionine synthase. CblD, CblC, and the activation domain of methionine synthase share several distinguishing features and, together with two recently described corrinoid-dependent reductive dehalogenases, constitute a new subclass within the nitro-FMN reductase superfamily. We demonstrate that CblD enhances oxidation of cob(II)alamin bound to CblC and that disease-causing mutations in CblD impair the kinetics of this reaction. The striking structural similarity of CblD to CblC, believed to be contiguous in the cobalamin trafficking pathway, suggests the co-option of molecular mimicry as a strategy for achieving its function.
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Affiliation(s)
- Kazuhiro Yamada
- From the Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814 and
| | - Carmen Gherasim
- the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600
| | - Ruma Banerjee
- the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600, To whom correspondence may be addressed. Tel.: 734-615-5238; E-mail:
| | - Markos Koutmos
- From the Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814 and , To whom correspondence may be addressed. Tel.: 301-295-9419; E-mail:
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27
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Karasik A, Shanmuganathan A, Howard MJ, Fierke CA, Koutmos M. Nuclear Protein-Only Ribonuclease P2 Structure and Biochemical Characterization Provide Insight into the Conserved Properties of tRNA 5' End Processing Enzymes. J Mol Biol 2015; 428:26-40. [PMID: 26655022 DOI: 10.1016/j.jmb.2015.11.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 11/03/2015] [Accepted: 11/10/2015] [Indexed: 10/22/2022]
Abstract
Protein-only RNase Ps (PRORPs) are a recently discovered class of RNA processing enzymes that catalyze maturation of the 5' end of precursor tRNAs in Eukaryotes. PRORPs are found in the nucleus and/or organelles of most eukaryotic organisms. Arabidopsis thaliana is a representative organism that contains PRORP enzymes (PRORP1, PRORP2 and PRORP3) in both its nucleus and its organelles; PRORP2 and PRORP3 localize to the nucleus and PRORP1 localizes to the chloroplast and the mitochondria. Apart from their identification, almost nothing is known about the structure and function of PRORPs that act in the nucleus. Here, we use a combination of biochemical assays and X-ray crystallography to characterize A. thaliana PRORP2. We solved the crystal structure of PRORP2 (3.2Å) revealing an overall V-shaped protein and conserved metallonuclease active-site structure. Our biochemical studies indicate that PRORP2 requires Mg(2+) for catalysis and catalyzes the maturation of nuclear encoded substrates up to 10-fold faster than mitochondrial encoded precursor nad6 t-element under single-turnover conditions. We also demonstrate that PRORP2 preferentially binds precursor tRNAs containing short 5' leaders and 3' trailers; however, leader and trailer lengths do not significantly alter the observed rate constants of PRORP2 in single-turnover cleavage assays. Our data provide a biochemical and structural framework to begin understanding how nuclear localized PRORPs recognize and cleave their substrates.
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Affiliation(s)
- Agnes Karasik
- Department of Biochemistry, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 28104, USA
| | - Aranganathan Shanmuganathan
- Department of Biochemistry, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 28104, USA
| | - Michael J Howard
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Carol A Fierke
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA; Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Markos Koutmos
- Department of Biochemistry, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 28104, USA.
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28
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Ganu RS, Ishida Y, Koutmos M, Kolokotronis SO, Roca AL, Garrow TA, Schook LB. Evolutionary Analyses and Natural Selection of Betaine-Homocysteine S-Methyltransferase (BHMT) and BHMT2 Genes. PLoS One 2015. [PMID: 26213999 PMCID: PMC4516251 DOI: 10.1371/journal.pone.0134084] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Betaine-homocysteine S-methyltransferase (BHMT) and BHMT2 convert homocysteine to methionine using betaine and S-methylmethionine, respectively, as methyl donor substrates. Increased levels of homocysteine in blood are associated with cardiovascular disease. Given their role in human health and nutrition, we identified BHMT and BHMT2 genes and proteins from 38 species of deuterostomes including human and non-human primates. We aligned the genes to look for signatures of selection, to infer evolutionary rates and events across lineages, and to identify the evolutionary timing of a gene duplication event that gave rise to two genes, BHMT and BHMT2. We found that BHMT was present in the genomes of the sea urchin, amphibians, reptiles, birds and mammals; BHMT2 was present only across mammals. BHMT and BHMT2 were present in tandem in the genomes of all monotreme, marsupial and placental species examined. Evolutionary rates were accelerated for BHMT2 relative to BHMT. Selective pressure varied across lineages, with the highest dN/dS ratios for BHMT and BHMT2 occurring immediately following the gene duplication event, as determined using GA Branch analysis. Nine codons were found to display signatures suggestive of positive selection; these contribute to the enzymatic or oligomerization domains, suggesting involvement in enzyme function. Gene duplication likely occurred after the divergence of mammals from other vertebrates but prior to the divergence of extant mammalian subclasses, followed by two deletions in BHMT2 that affect oligomerization and methyl donor specificity. The faster evolutionary rate of BHMT2 overall suggests that selective constraints were reduced relative to BHMT. The dN/dS ratios in both BHMT and BHMT2 was highest following the gene duplication, suggesting that purifying selection played a lesser role as the two paralogs diverged in function.
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Affiliation(s)
- Radhika S. Ganu
- Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
| | - Yasuko Ishida
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
| | - Markos Koutmos
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, United States of America
| | | | - Alfred L. Roca
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
| | - Timothy A. Garrow
- Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
| | - Lawrence B. Schook
- Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
- * E-mail:
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29
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Mládková J, Hladílková J, Diamond CE, Tryon K, Yamada K, Garrow TA, Jungwirth P, Koutmos M, Jiráček J. Specific potassium ion interactions facilitate homocysteine binding to betaine-homocysteine S
-methyltransferase. Proteins 2014; 82:2552-64. [DOI: 10.1002/prot.24619] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 05/24/2014] [Accepted: 05/28/2014] [Indexed: 12/17/2022]
Affiliation(s)
- Jana Mládková
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic; v.v.i., Flemingovo nám. 2, 166 10 Prague 6 Czech Republic
| | - Jana Hladílková
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic; v.v.i., Flemingovo nám. 2, 166 10 Prague 6 Czech Republic
| | - Carrie E. Diamond
- Department of Food Science and Human Nutrition; University of Illinois; Urbana Illinois 61801
| | - Katherine Tryon
- Department of Food Science and Human Nutrition; University of Illinois; Urbana Illinois 61801
| | - Kazuhiro Yamada
- Department of Biochemistry and Molecular Biology; Uniformed Services University of the Health Sciences; Bethesda Maryland 20814
| | - Timothy A. Garrow
- Department of Food Science and Human Nutrition; University of Illinois; Urbana Illinois 61801
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic; v.v.i., Flemingovo nám. 2, 166 10 Prague 6 Czech Republic
| | - Markos Koutmos
- Department of Biochemistry and Molecular Biology; Uniformed Services University of the Health Sciences; Bethesda Maryland 20814
| | - Jiří Jiráček
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic; v.v.i., Flemingovo nám. 2, 166 10 Prague 6 Czech Republic
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30
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Lofgren M, Koutmos M, Banerjee R. Autoinhibition and signaling by the switch II motif in the G-protein chaperone of a radical B12 enzyme. J Biol Chem 2013; 288:30980-9. [PMID: 23996001 DOI: 10.1074/jbc.m113.499970] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MeaB is an accessory GTPase protein involved in the assembly, protection, and reactivation of 5'-deoxyadenosyl cobalamin-dependent methylmalonyl-CoA mutase (MCM). Mutations in the human ortholog of MeaB result in methylmalonic aciduria, an inborn error of metabolism. G-proteins typically utilize conserved switch I and II motifs for signaling to effector proteins via conformational changes elicited by nucleotide binding and hydrolysis. Our recent discovery that MeaB utilizes an unusual switch III region for bidirectional signaling with MCM raised questions about the roles of the switch I and II motifs in MeaB. In this study, we addressed the functions of conserved switch II residues by performing alanine-scanning mutagenesis. Our results demonstrate that the GTPase activity of MeaB is autoinhibited by switch II and that this loop is important for coupling nucleotide-sensitive conformational changes in switch III to elicit the multiple chaperone functions of MeaB. Furthermore, we report the structure of MeaB·GDP crystallized in the presence of AlFx(-) to form the putative transition state analog, GDP·AlF4(-). The resulting crystal structure and its comparison with related G-proteins support the conclusion that the catalytic site of MeaB is incomplete in the absence of the GTPase-activating protein MCM and therefore unable to stabilize the transition state analog. Favoring an inactive conformation in the absence of the client MCM protein might represent a strategy for suppressing the intrinsic GTPase activity of MeaB in which the switch II loop plays an important role.
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Affiliation(s)
- Michael Lofgren
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600 and
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31
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Ganu R, Garrow T, Koutmos M, Rund L, Schook LB. Splicing variants of the porcine betaine-homocysteine S-methyltransferase gene: implications for mammalian metabolism. Gene 2013; 529:228-37. [PMID: 23948084 DOI: 10.1016/j.gene.2013.07.103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Revised: 07/23/2013] [Accepted: 07/30/2013] [Indexed: 12/18/2022]
Abstract
Betaine-homocysteine S-methyltransferase (BHMT) activity is only detected in the liver of rodents, but in both the liver and kidney cortex of humans and pigs; therefore, the pig was chosen as a model to define the spatial and temporal expression of BHMT during development. During fetal development, a total of ten splice variants of bhmt were expressed at varying levels across a wide range of porcine tissues. Two variants contained an identical ORF that encoded a C-terminal truncated form of BHMT (tBHMT). The bhmt transcripts were expressed at significant levels in the liver and kidney from day 45 of gestation (G45) onward. The transcripts encoding tBHMT represented 5-13% of the total bhmt transcripts in G30 fetus, G45 liver, and adult liver and kidney cortex. The dominant structural feature of wild type BHMT is an (βα)8 barrel, however, a modeled structure of tBHMT suggests that this protein would assume a horseshoe fold and lack methyltransferase activity. Low BHMT activity was detected in the G30 fetus, and slightly increased levels of activity were observed in the liver from G45 and G90 fetuses. The bhmt promoter contained three key CpG sites, and methylation of these sites was significantly higher in adult lung compared to adult liver. The data reported herein suggest that genomic DNA methylation and variation of the 5' and 3' UTRs of bhmt transcripts are key regulators for the level of BHMT transcription and translation.
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Affiliation(s)
- Radhika Ganu
- Division of Nutritional Sciences, University of Illinois, Urbana, IL 61801, USA
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Yadav PK, Yamada K, Chiku T, Koutmos M, Banerjee R. Structure and kinetic analysis of H2S production by human mercaptopyruvate sulfurtransferase. J Biol Chem 2013; 288:20002-13. [PMID: 23698001 PMCID: PMC3707699 DOI: 10.1074/jbc.m113.466177] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Mercaptopyruvate sulfurtransferase (MST) is a source of endogenous H2S, a gaseous signaling molecule implicated in a wide range of physiological processes. The contribution of MST versus the other two H2S generators, cystathionine β-synthase and γ-cystathionase, has been difficult to evaluate because many studies on MST have been conducted at high pH and have used varied reaction conditions. In this study, we have expressed, purified, and crystallized human MST in the presence of the substrate 3-mercaptopyruvate (3-MP). The kinetics of H2S production by MST from 3-MP was studied at pH 7.4 in the presence of various physiological persulfide acceptors: cysteine, dihydrolipoic acid, glutathione, homocysteine, and thioredoxin, and in the presence of cyanide. The crystal structure of MST reveals a mixture of the product complex containing pyruvate and an active site cysteine persulfide (Cys(248)-SSH) and a nonproductive intermediate in which 3-MP is covalently linked via a disulfide bond to an active site cysteine. The crystal structure analysis allows us to propose a detailed mechanism for MST in which an Asp-His-Ser catalytic triad is positioned to activate the nucleophilic cysteine residue and participate in general acid-base chemistry, whereas our kinetic analysis indicates that thioredoxin is likely to be the major physiological persulfide acceptor for MST.
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Affiliation(s)
- Pramod Kumar Yadav
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600 and
| | - Kazuhiro Yamada
- the Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 28104
| | - Taurai Chiku
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600 and
| | - Markos Koutmos
- the Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 28104
| | - Ruma Banerjee
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600 and , To whom correspondence should be addressed: 3320B MSRB III, 1150 W. Medical Center Dr., University of Michigan, Ann Arbor, MI 48109-0600. Tel.: 734-615-5238; E-mail:
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Howard MJ, Liu X, Lim WH, Klemm BP, Fierke CA, Koutmos M, Engelke DR. RNase P enzymes: divergent scaffolds for a conserved biological reaction. RNA Biol 2013; 10:909-14. [PMID: 23595059 DOI: 10.4161/rna.24513] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Ribonuclease P (RNase P) catalyzes the maturation of the 5' end of precursor-tRNAs (pre-tRNA) and is conserved in all domains of life. However, the composition of RNase P varies from bacteria to archaea and eukarya, making RNase P one of the most diverse enzymes characterized. Most known RNase P enzymes contain a large catalytic RNA subunit that associates with one to 10 proteins. Recently, a protein-only form of RNase P was discovered in mitochondria and chloroplasts of many higher eukaryotes. This proteinaceous RNase P (PRORP) represents a new class of metallonucleases. Here we discuss our recent crystal structure of PRORP1 from Arabidopsis thaliana and speculate on the reasons for the replacement of catalytic RNA by a protein catalyst. We conclude, based on an analysis of the catalytic efficiencies of ribonucleoprotein (RNP) and PRORP enzymes, that the need for greater catalytic efficiency is most likely not the driving force behind the replacement of the RNA with a protein catalyst. The emergence of a protein-based RNase P more likely reflects the increasing complexity of the biological system, including difficulties in importation into organelles and vulnerability of organellar RNAs to cleavage.
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Affiliation(s)
- Michael J Howard
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
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Abstract
An early step in the intracellular processing of vitamin B(12) involves CblC, which exhibits dual reactivity, catalyzing the reductive decyanation of cyanocobalamin (vitamin B(12)), and the dealkylation of alkylcobalamins (e.g. methylcobalamin; MeCbl). Insights into how the CblC scaffold supports this chemical dichotomy have been unavailable despite it being the most common locus of patient mutations associated with inherited cobalamin disorders that manifest in both severe homocystinuria and methylmalonic aciduria. Herein, we report structures of human CblC, with and without bound MeCbl, which provide novel biochemical insights into its mechanism of action. Our results reveal that CblC is the most divergent member of the NADPH-dependent flavin reductase family and can use FMN or FAD as a prosthetic group to catalyze reductive decyanation. Furthermore, CblC is the first example of an enzyme with glutathione transferase activity that has a sequence and structure unrelated to the GST superfamily. CblC thus represents an example of evolutionary adaptation of a common structural platform to perform diverse chemistries. The CblC structure allows us to rationalize the biochemical basis of a number of pathological mutations associated with severe clinical phenotypes.
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Affiliation(s)
- Markos Koutmos
- Department of Biological Chemistry and the Life Sciences Institute, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600, USA
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Hsieh J, Koutmou KS, Rueda D, Koutmos M, Walter NG, Fierke CA. A divalent cation stabilizes the active conformation of the B. subtilis RNase P x pre-tRNA complex: a role for an inner-sphere metal ion in RNase P. J Mol Biol 2010; 400:38-51. [PMID: 20434461 PMCID: PMC2939038 DOI: 10.1016/j.jmb.2010.04.050] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Revised: 04/22/2010] [Accepted: 04/24/2010] [Indexed: 01/25/2023]
Abstract
Metal ions interact with RNA to enhance folding, stabilize structure, and, in some cases, facilitate catalysis. Assigning functional roles to specifically bound metal ions presents a major challenge in analyzing the catalytic mechanisms of ribozymes. Bacillus subtilis ribonuclease P (RNase P), composed of a catalytically active RNA subunit (PRNA) and a small protein subunit (P protein), catalyzes the 5'-end maturation of precursor tRNAs (pre-tRNAs). Inner-sphere coordination of divalent metal ions to PRNA is essential for catalytic activity but not for the formation of the RNase P x pre-tRNA (enzyme-substrate, ES) complex. Previous studies have demonstrated that this ES complex undergoes an essential conformational change (to the ES* conformer) before the cleavage step. Here, we show that the ES* conformer is stabilized by a high-affinity divalent cation capable of inner-sphere coordination, such as Ca(II) or Mg(II). Additionally, a second, lower-affinity Mg(II) activates cleavage catalyzed by RNase P. Structural changes that occur upon binding Ca(II) to the ES complex were determined by time-resolved Förster resonance energy transfer measurements of the distances between donor-acceptor fluorophores introduced at specific locations on the P protein and pre-tRNA 5' leader. These data demonstrate that the 5' leader of pre-tRNA moves 4 to 6 A closer to the PRNA x P protein interface during the ES-to-ES* transition and suggest that the metal-dependent conformational change reorganizes the bound substrate in the active site to form a catalytically competent ES* complex.
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Affiliation(s)
- John Hsieh
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan
| | | | - David Rueda
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan
| | - Markos Koutmos
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan
| | - Nils G. Walter
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan
| | - Carol A. Fierke
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan
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Vanek V, Budesínský M, Kabeleová P, Sanda M, Kozísek M, Hanclová I, Mládková J, Brynda J, Rosenberg I, Koutmos M, Garrow TA, Jirácek J. Structure-activity study of new inhibitors of human betaine-homocysteine S-methyltransferase. J Med Chem 2009; 52:3652-65. [PMID: 19534555 DOI: 10.1021/jm8015798] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Betaine-homocysteine S-methyltransferase (BHMT) catalyzes the transfer of a methyl group from betaine to l-homocysteine, yielding dimethylglycine and l-methionine. In this study, we prepared a new series of BHMT inhibitors. The inhibitors were designed to mimic the hypothetical transition state of BHMT substrates and consisted of analogues with NH, N(CH(3)), or N(CH(3))(2) groups separated from the homocysteine sulfur atom by a methylene, ethylene, or a propylene spacer. Only the inhibitor with the N(CH(3)) moiety and ethylene spacer gave moderate inhibition. This result led us to prepare two inhibitors lacking a nitrogen atom in the S-linked alkyl chain: (RS,RS)-5-(3-amino-3-carboxypropylthio)-3-methylpentanoic acid and (RS)-5-(3-amino-3-carboxypropylthio)-3,3-dimethylpentanoic acid. Both of these compounds were highly potent inhibitors of BHMT. The finding that BHMT does not tolerate a true betaine mimic within these inhibitors, especially the nitrogen atom, is surprising and evokes questions about putative conformational changes of BHMT upon the binding of the substrates/products and inhibitors.
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Affiliation(s)
- Václav Vanek
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic
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Abstract
Methyltransferases that employ cobalamin cofactors, or their analogs the cobamides, as intermediates in catalysis of methyl transfer play vital roles in energy generation in anaerobic unicellular organisms. In a broader range of organisms they are involved in the conversion of homocysteine to methionine. Although the individual methyl transfer reactions catalyzed are simple S(N)2 displacements, the required change in coordination at the cobalt of the cobalamin or cobamide cofactors and the lability of the reduced Co(+1) intermediates introduces the necessity for complex conformational changes during the catalytic cycle. Recent spectroscopic and structural studies on several of these methyltransferases have helped to reveal the strategies by which these conformational changes are facilitated and controlled.
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Affiliation(s)
- Rowena G Matthews
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109-2216, USA.
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Szegedi SS, Castro CC, Koutmos M, Garrow TA. Betaine-homocysteine S-methyltransferase-2 is an S-methylmethionine-homocysteine methyltransferase. J Biol Chem 2008; 283:8939-45. [PMID: 18230605 PMCID: PMC2276374 DOI: 10.1074/jbc.m710449200] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Revised: 01/28/2008] [Indexed: 11/06/2022] Open
Abstract
We demonstrate that purified recombinant human betainehomocysteine methyltransferase-2 (BHMT-2) is a zinc metalloenzyme that uses S-methylmethionine (SMM) as a methyl donor for the methylation of homocysteine. Unlike the highly homologous betaine-homocysteine methyltransferase (BHMT), BHMT-2 cannot use betaine. The K(m) of BHMT-2 for SMM was determined to be 0.94 mm, and it has a turnover number similar to BHMT. Several compounds were tested as inhibitors of recombinant human BHMT and BHMT-2. The SMM-specific methyltransferase activity of BHMT-2 is not inhibited by dimethylglycine and betaine, whereas the former is a potent inhibitor of BHMT. Methionine is a stronger inhibitor of BHMT-2 than BHMT, and S-adenosylmethionine does not inhibit BHMT but is a weak inhibitor of BHMT-2. BHMT can use SMM as a methyl donor with a k(cat)/K(m) that is 5-fold lower than the k(cat)/K(m) for betaine. However, SMM does not inhibit BHMT activity when it is presented to the enzyme at concentrations that are 10-fold greater than the subsaturating amounts of betaine used in the assay. Based on these data, it is our current hypothesis that in vivo most if not all of the SMM-dependent methylation of homocysteine occurs via BHMT-2.
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Affiliation(s)
- Sandra S Szegedi
- Departments of Animal Science and Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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39
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Koutmos M, Georgakaki IP, Coucouvanis D. Borohydride, azide, and chloride anions as terminal ligands on Fe/Mo/S clusters. Synthesis, structure and characterization of [(Cl4-cat)(PPr3) MoFe3S4(X)2]2(Bu4N)4 and [(Cl4-cat)(PPr3)MoFe3S4 (PPr3)(X)]2(Bu4N)2 (X = N3-, BH4-, Cl-) double-fused cubanes. NMR reactivity studies of [(Cl4-cat)(PPr3) MoFe3S4(BH4)2]2(Bu4N)4. Inorg Chem 2006; 45:3648-56. [PMID: 16634597 DOI: 10.1021/ic052156b] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Our explorations of the reactivity of Fe/Mo/S clusters of some relevance to the FeMoco nitrogenase have led to new double-fused cubane clusters with the Mo2Fe6S8 core as derivatives of the known (Cl4-cat)2Mo2Fe6S8(PPr3)6 (I) fused double cubane. The new clusters have been obtained by substitution reactions of the PPr3 ligands with Cl-, BH4-, and N3-. By careful control of the conditions of these reactions, the clusters [(Cl4-cat)(PPr3)MoFe3S4(BH4)2]2(Bu4N)4 (II), [(Cl4-cat)(PPr3)MoFe3S4(PPr3)(BH4)]2(Bu4N)2 (III), [(Cl4-cat)(PPr3)MoFe3S4(N3)2]2(Bu4N)4 (IV), [(Cl4-cat)(PPr3)MoFe3S4(PPr3)(N3)]2(Bu4N)2 (V), and [(Cl4-cat)(PPr3)MoFe3S4Cl2]2(Et4N)4 (VI) have been obtained and structurally characterized. A study of their electrochemistry shows that the reduction potentials for the derivatives of I are shifted to more positive values than those of I, suggesting a stabilization of the reduced clusters by the anionic ligands BH4- and N3-. Using 1H NMR spectroscopy, we have explored the lability of the BH4- ligand in II in coordinating solvents and its hydridic character, which is apparent in its reactivity toward proton sources such as MeOH or PhOH.
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Affiliation(s)
- Markos Koutmos
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
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Xiao Y, Koutmos M, Case DA, Coucouvanis D, Wang H, Cramer SP. Dynamics of an [Fe4S4(SPh)4]2- cluster explored via IR, Raman, and nuclear resonance vibrational spectroscopy (NRVS)-analysis using 36S substitution, DFT calculations, and empirical force fields. Dalton Trans 2006:2192-201. [PMID: 16673033 DOI: 10.1039/b513331a] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have used four vibrational spectroscopies--FT-IR, FT-Raman, resonance Raman, and 57Fe nuclear resonance vibrational spectroscopy (NRVS)--to study the normal modes of the Fe-S cluster in [(n-Bu)4N]2[Fe4S4(SPh)4]. This [Fe4S4(SR)4]2- complex serves as a model for the clusters in 4Fe ferredoxins and high-potential iron proteins (HiPIPs). The IR spectra exhibited differences above and below the 243 K phase transition. Significant shifts with 36S substitution into the bridging S positions were also observed. The NRVS results were in good agreement with the low temperature data from the conventional spectroscopies. The NRVS spectra were interpreted by normal mode analysis using optimized Urey-Bradley force fields (UBFF) as well as from DFT theory. For the UBFF calculations, the parameters were refined by comparing calculated and observed NRVS frequencies and intensities. The frequency shifts after 36S substitution were used as an additional constraint. A D 2d symmetry Fe4S4S'4 model could explain most of the observed frequencies, but a better match to the observed intensities was obtained when the ligand aromatic rings were included for a D 2d Fe4S4(SPh)4 model. The best results were obtained using the low temperature structure without symmetry constraints. In addition to stretching and bending vibrations, low frequency modes between approximately 50 and 100 cm(-1) were observed. These modes, which have not been seen before, are interpreted as twisting motions with opposing sides of the cube rotating in opposite directions. In contrast with a recent paper on a related Fe4S4 cluster, we find no need to assign a large fraction of the low frequency NRVS intensity to 'rotational lattice modes'. We also reassign the 430 cm(-1) band as primarily an elongation of the thiophenolate ring, with approximately 10% terminal Fe-S stretch character. This study illustrates the benefits of combining NRVS with conventional Raman and IR analysis for characterization of Fe-S centers. DFT theory is shown to provide remarkable agreement with the experimental NRVS data. These results provide a reference point for the analysis of more complex Fe-S clusters in proteins.
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Affiliation(s)
- Yuming Xiao
- Department of Applied Science, University of California, Davis, CA 95616, USA
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42
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Abstract
The reactivity of Fe/S and Fe/Mo/S clusters, similar or analogous to those occurring in biological systems, with thiophilic metal ions has not been explored. In this Communication, we demonstrate that synthesis of heteropolynuclear clusters with different coordination geometries for different metals at different sites is possible by metal substitution or by metal addition reactions. The two clusters we report herein ([(Cl4-cat)2Mo2Cu5Fe4S9(PnPr3)7(SPnPr3)2]PF6 and [(Cl4-cat)2Mo2Cu6Fe4S10(PnPr3)8]) contain Fe, Mo, and Cu, which display pseudotetrahedral, pseudooctahedral, and pseudotrigonal geometries, respectively. The synthesis of these clusters is achieved by the addition of appropriate amounts of [Cu(CH3CN)4]+ to [(Cl4-cat)2Mo2Fe8(PnPr3)6]. The formation of the different products is temperature- and solvent-dependent. The Cu(I) units incorporated into the metal cluster framework, either bind to available lone pairs of the already bridging S ligands or displace the less thiophilic Fe atoms. Among the essential features of these new molecules are recognizable Fe/S fragments including an Fe6S9 core in the first cluster and the pentlandite Fe4Cu4S6 core in the second cluster.
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Affiliation(s)
- Markos Koutmos
- Department of Chemistry, The University of Michigan, Ann Arbor, 48109, USA
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Smith MC, Xiao Y, Wang H, George SJ, Coucouvanis D, Koutmos M, Sturhahn W, Alp EE, Zhao J, Cramer SP. Normal-mode analysis of FeCl4- and Fe2S2Cl42- via vibrational mössbauer, resonance Raman, and FT-IR spectroscopies. Inorg Chem 2005; 44:5562-70. [PMID: 16060605 DOI: 10.1021/ic0482584] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[NEt(4)][FeCl(4)], [P(C(6)H(5))(4)][FeCl(4)], and [NEt(4)](2)[Fe(2)S(2)Cl(4)] have been examined using (57)Fe nuclear resonance vibrational spectroscopy (NRVS). These complexes serve as simple models for Fe-S clusters in metalloproteins. The (57)Fe partial vibrational density of states (PVDOS) spectra were interpreted by computation of the normal modes assuming Urey-Bradley force fields, using additional information from infrared and Raman spectra. Previously published force constants were used as initial values; the new constraints from NRVS frequencies and amplitudes were then used to refine the force field parameters in a nonlinear least-squares analysis. The normal-mode calculations were able to quantitatively reproduce both the frequencies and the amplitudes of the intramolecular-mode (57)Fe PVDOS. The optimized force constants for bending, stretching, and nonbonded interactions agree well with previously reported values. In addition, the NRVS technique also allowed clear observation of anion-cation lattice modes below 100 cm(-1) that are nontrivial to observe by conventional spectroscopies. These features were successfully reproduced, either by assuming whole-body motions of point-mass anions and cations or by simulations using all of the atoms in the unit cell. The advantages of a combined NRVS, Raman, and IR approach to characterization of Fe-S complexes are discussed.
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Affiliation(s)
- Matt C Smith
- Department of Applied Science, University of California, Davis, 95616, USA
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44
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Koutmos M, Coucouvanis D. Metal Clusters as Ligands: Substitution of Fe ions in Fe/Mo/S Clusters by Thiophilic CuI Ions To Give Clusters with [Cu4Mo2Fe2S8]4+ and [Cu5Mo3Fe4S11]6+ Cores. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200462596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Koutmos M, Coucouvanis D. Metal Clusters as Ligands: Substitution of Fe ions in Fe/Mo/S Clusters by Thiophilic CuI Ions To Give Clusters with [Cu4Mo2Fe2S8]4+ and [Cu5Mo3Fe4S11]6+ Cores. Angew Chem Int Ed Engl 2005; 44:1971-4. [PMID: 15724256 DOI: 10.1002/anie.200462596] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Markos Koutmos
- Department Of Chemistry, The University Of Michigan, Ann Arbor, MI 48109-1055, USA
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Koutmos M, Kalyvas H, Sanakis Y, Simopoulos A, Coucouvanis D. Systematic Synthesis of Heterometallic Ni/Fe/S and Cu/Fe/S Clusters with a Pentlandite-like M8S6 Core. J Am Chem Soc 2005; 127:3706-7. [PMID: 15771499 DOI: 10.1021/ja042938o] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The systematic synthesis of heterometallic Ni/Fe/S and Cu/Fe/S clusters with a M8S6 core structure that resembles that of pentlandite minerals is described. The chemical properties and electronic structures of the new clusters have been investigated and are reported in this communication.
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Affiliation(s)
- Markos Koutmos
- Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109, USA
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Affiliation(s)
- Markos Koutmos
- 930 North University, Department Of Chemistry, The University Of Michigan, Ann Arbor, MI 48109-1055, USA
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Koutmos M, Coucouvanis D. Borohydride Anions as Terminal Ligands on a Fe/Mo/S Cluster. Synthesis, Structure, and Characterization of the [(Cl4-cat)(PPr3)MoFe3S4(BH4)2]2(Bu4N)4 Double-Fused Cubane. Inorg Chem 2004; 43:6508-10. [PMID: 15476337 DOI: 10.1021/ic049275w] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The synthesis and structure of the first Mo/Fe/S/BH(4) cluster is reported. Reaction of (Cl(4)-cat)(2)Mo(2)Fe(6)S(8)(PPr(3))(6) with 4 equiv of Bu(4)NBH(4) results in the formation of [(Cl(4)-cat)(PPr(3))MoFe(3)S(4)(BH(4))(2)](2)(Bu(4)N)(4) (Cl(4)-cat = tetrachloro-catecholate) which has been fully characterized. X-ray structural determination of this double-fused cubane reveals four BH(4)(-) ligands bound to four Fe atoms in a bidentate fashion. A synopsis of the solution characterization as well as the reactivity of this cluster is also presented.
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Affiliation(s)
- Markos Koutmos
- Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109, USA
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50
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Han J, Koutmos M, Ahmad SA, Coucouvanis D. Rational synthesis of high nuclearity Mo/Fe/S clusters: the reductive coupling approach in the convenient synthesis of (Cl(4)-cat)(2)Mo(2)Fe(6)S(8)(PR(3))(6) [R = Et, (n)Pr, (n)Bu] and the new [(Cl(4)-cat)(2)Mo(2)Fe(2)S(3)O(PEt(3))(3)Cl]-1/2(Fe(PEt(3))(2)(MeCN)(4)) and (Cl(4)-cat)(2)Mo(2)Fe(3)S(5)(PEt(3))(5) clusters. Inorg Chem 2001; 40:5985-99. [PMID: 11681915 DOI: 10.1021/ic0104914] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A general method for the synthesis of high nuclearity Mo/Fe/S clusters is presented and involves the reductive coupling of the (Et(4)N)(2)[(Cl(4)-cat)MoOFeS(2)Cl(2)] (I) and (Et(4)N)(2)[Fe(2)S(2)Cl(4)] (II) clusters. The reaction of I and II with Fe(PR(3))(2)Cl(2) or sodium salts of noncoordinating anions such as NaPF(6) or NaBPh(4) in the presence of PR(3) (R = Et, (n)Pr, or (n)Bu) affords (Cl(4)-cat)(2)Mo(2)Fe(6)S(8)(PR(3))(6) [R = Et (IIIa), (n)Pr (IIIb), (n)Bu (IIIc)], Fe(6)S(6)(PEt(3))(4)Cl(2) (IV) and (PF(6))[Fe(6)S(8)(P(n)Pr(3))(6)] (V) as byproducts. The isolation of (Et(4)N)[Fe(PEt(3))Cl(3)] (VI), NaCl, and SPEt(3) supports a reductive coupling mechanism. Cluster IV and V also have been synthesized by the reductive self-coupling of compound II. The reductive coupling reaction between I and II by PEt(3) and NaPF(6) in a 1:1 ratio produces the (Et(4)N)(2)[(Cl(4)-cat)Mo(L)Fe(3)S(4)Cl(3)] clusters [L = MeCN (VIIa), THF (VIIb)]. The hitherto unknown [(Cl(4)-cat)(2)Mo(2)Fe(2)S(3)O(PEt(3))(3)Cl](+) cluster (VIII) has been isolated as the 2:1 salt of the (Fe(PEt(3))(2)(MeCN)(4))(2+) cation after the reductive self-coupling reaction of I in the presence of Fe(PEt(3))(2)Cl(2). Cluster VIII crystallizes in the monoclinic space group P2(1)/c with a = 11.098(3) A, b = 22.827(6) A, c = 25.855(6) A, beta = 91.680(4) degrees, and Z = 4. The formal oxidation states of metal atoms in VIII have been assigned as Mo(III), Mo(IV), Fe(II), and Fe(III) on the basis of zero-field Mössbauer spectra. The Fe(PEt(3))(2)(MeCN)(4) cation of VIII is also synthesized independently, isolated as the BPh(4)(-) salt (IX), and has been structurally characterized. The reductive coupling of compound I also affords in low yield the new (Cl(4)-cat)(2)Mo(2)Fe(3)S(5)(PEt(3))(5) cluster (X) as a byproduct. Cluster X crystallizes in the monoclinic space group P2(1)/n with a = 14.811(3) A, b = 22.188(4) A, c = 21.864(4) A, beta = 100.124(3) degrees, and Z = 4 and the structure shows very short Mo-Fe, Fe-Fe, Mo-S, Fe-S bonds. The oxidation states of the metal atoms in this neutral cluster (X) have been assigned as Mo(IV)Mo(III)Fe(II)Fe(II)Fe(III) based on zero-field Mössbauer and magnetic measurement. All Fe atoms are high spin and two of the three Fe-Fe distances are found at 2.4683(9) A and 2.4721(9) A.
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Affiliation(s)
- J Han
- Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
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