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Mascarenhas R, Guha A, Li Z, Ruetz M, An S, Seravalli J, Banerjee R. Cobalt-Sulfur Coordination Chemistry Drives B 12 Loading onto Methionine Synthase. J Am Chem Soc 2023:10.1021/jacs.3c07941. [PMID: 37916782 PMCID: PMC11063128 DOI: 10.1021/jacs.3c07941] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2023]
Abstract
Cobalt-sulfur (Co-S) coordination is labile to both oxidation and reduction chemistry and is rarely seen in nature. Cobalamin (or vitamin B12) is an essential cobalt-containing organometallic cofactor in mammals and is escorted via an intricate network of chaperones to a single cytoplasmic target, methionine synthase. In this study, we report that the human cobalamin trafficking protein, MMADHC, exploits the chemical lability of Co-S coordination for cofactor off-loading onto methionine synthase. Cys-261 on MMADHC serves as the β-axial ligand to cobalamin. Complex formation between MMADHC and methionine synthase is signaled by loss of the lower axial nitrogen ligand, leading to five-coordinate thiolato-cobalamin. Nucleophilic displacement by the vicinal thiolate, Cys-262, completes cofactor transfer to methionine synthase and release of a cysteine disulfide-containing MMADHC. The physiological relevance of this mechanism is supported by clinical variants of MMADHC, which impair cofactor binding and off-loading, explaining the molecular basis of the associated homocystinuria.
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Affiliation(s)
- Romila Mascarenhas
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Arkajit Guha
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Zhu Li
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Markus Ruetz
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Sojin An
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Javier Seravalli
- Department of Biological Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Ruma Banerjee
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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2
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Gouda H, Li Z, Ruetz M, Banerjee R. Coordination Chemistry Controls Coenzyme B 12 Synthesis by Human Adenosine Triphosphate:Cob(I)alamin Adenosyltransferase. Inorg Chem 2023; 62:12630-12633. [PMID: 37526260 PMCID: PMC10507449 DOI: 10.1021/acs.inorgchem.3c02163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2023]
Abstract
Cobalamin (or vitamin B12)-dependent enzymes and trafficking chaperones exploit redox-linked coordination chemistry to control the cofactor reactivity during catalysis and translocation. As the cobalt oxidation state decreases from 3+ to 1+, the preferred cobalamin geometry changes from six- to four-coordinate (4-c). In this study, we reveal the sizable thermodynamic gain that accrues for human adenosine triphosphate (ATP):cob(I)alamin adenosyltransferase (or MMAB) by enforcing an unfavorable 4-c cob(II)alamin geometry. MMAB-bound cob(II)alamin is reduced to the supernucleophilic cob(I)alamin intermediate during the synthesis of 5'-deoxyadenosylcobalamin. Herein, we report the first experimentally determined reduction potential for 4-c cob(II)alamin (-325 ± 9 mV), which is 180 mV more positive than for the five-coordinate (5-c) water-liganded species. The redox potential of MMAB-bound cob(II)alamin is within the range of adrenodoxin, which we demonstrate functions as an electron donor. We also show that stabilization of 5-c cob(II)alamin by a subset of MMAB patient variants compromises the reduction by adrenodoxin, explaining the underlying pathogenic mechanism.
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Affiliation(s)
- Harsha Gouda
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109 USA
| | - Zhu Li
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109 USA
| | - Markus Ruetz
- Department of Biological Chemistry, 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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3
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Mascarenhas R, Guha A, Li Z, Ruetz M, An S, Seravalli J, Banerjee R. Cobalt-sulfur coordination chemistry drives B 12 loading onto methionine synthase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.25.550549. [PMID: 37546824 PMCID: PMC10402061 DOI: 10.1101/2023.07.25.550549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Cobalt-sulfur (Co-S) coordination is labile to both oxidation and reduction chemistry and is rarely seen in Nature. Cobalamin (or vitamin B 12 ) is an essential cobalt-containing organometallic cofactor in mammals, and is escorted via an intricate network of chaperones to a single cytoplasmic target, methionine synthase. In this study, we report that the human cobalamin trafficking protein, MMADHC, exploits the chemical lability of Co-S coordination, for cofactor off-loading onto methionine synthase. Cys-261 on MMADHC serves as the β-axial ligand to cobalamin. Complex formation between MMADHC and methionine synthase is signaled by loss of the lower axial nitrogen ligand, leading to five-coordinate thiolato-cobalamin. Nucleophilic displacement by the vicinal thiolate, Cys-262, completes cofactor transfer to methionine synthase and release of a cysteine disulfide-containing MMADHC. The physiological relevance of this mechanism is supported by clinical variants of MMADHC, which impair cofactor binding and off-loading, explaining the molecular basis of the associated homocystinuria.
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4
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Mascarenhas R, Ruetz M, Gouda H, Heitman N, Yaw M, Banerjee R. Architecture of the human G-protein-methylmalonyl-CoA mutase nanoassembly for B 12 delivery and repair. Nat Commun 2023; 14:4332. [PMID: 37468522 PMCID: PMC10356863 DOI: 10.1038/s41467-023-40077-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Accepted: 07/05/2023] [Indexed: 07/21/2023] Open
Abstract
G-proteins function as molecular switches to power cofactor translocation and confer fidelity in metal trafficking. The G-protein, MMAA, together with MMAB, an adenosyltransferase, orchestrate cofactor delivery and repair of B12-dependent human methylmalonyl-CoA mutase (MMUT). The mechanism by which the complex assembles and moves a >1300 Da cargo, or fails in disease, are poorly understood. Herein, we report the crystal structure of the human MMUT-MMAA nano-assembly, which reveals a dramatic 180° rotation of the B12 domain, exposing it to solvent. The complex, stabilized by MMAA wedging between two MMUT domains, leads to ordering of the switch I and III loops, revealing the molecular basis of mutase-dependent GTPase activation. The structure explains the biochemical penalties incurred by methylmalonic aciduria-causing mutations that reside at the MMAA-MMUT interfaces we identify here.
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Affiliation(s)
- Romila Mascarenhas
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Markus Ruetz
- 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
| | - Natalie Heitman
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Madeline Yaw
- Department of Biological Chemistry, 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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5
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Mascarenhas R, Ruetz M, Gouda H, Heitman N, Yaw M, Banerjee R. Architecture of the human G-protein-methylmalonyl-CoA mutase nanoassembly for B 12 delivery and repair. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.23.533963. [PMID: 36993209 PMCID: PMC10055420 DOI: 10.1101/2023.03.23.533963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
G-proteins function as molecular switches to power cofactor translocation and confer fidelity in metal trafficking. MMAA, a G-protein motor, together with MMAB, an adenosyltransferase, orchestrate cofactor delivery and repair of B 12 -dependent human methylmalonyl-CoA mutase (MMUT). The mechanism by which the motor assembles and moves a >1300 Da cargo, or fails in disease, are poorly understood. Herein, we report the crystal structure of the human MMUT-MMAA nanomotor assembly, which reveals a dramatic 180° rotation of the B 12 domain, exposing it to solvent. The nanomotor complex, stabilized by MMAA wedging between two MMUT domains, leads to ordering of the switch I and III loops, revealing the molecular basis of mutase-dependent GTPase activation. The structure explains the biochemical penalties incurred by methylmalonic aciduria-causing mutations that reside at the newly identified MMAA-MMUT interfaces.
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6
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McCorvie TJ, Ferreira D, Yue WW, Froese DS. The complex machinery of human cobalamin metabolism. J Inherit Metab Dis 2023; 46:406-420. [PMID: 36680553 DOI: 10.1002/jimd.12593] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 01/17/2023] [Accepted: 01/19/2023] [Indexed: 01/22/2023]
Abstract
Vitamin B12 (cobalamin, Cbl) is required as a cofactor by two human enzymes, 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR) and methylmalonyl-CoA mutase (MMUT). Within the body, a vast array of transporters, enzymes and chaperones are required for the generation and delivery of these cofactor forms. How they perform these functions is dictated by the structure and interactions of the proteins involved, the molecular bases of which are only now being elucidated. In this review, we highlight recent insights into human Cbl metabolism and address open questions in the field by employing a protein structure and interactome based perspective. We discuss how three very similar proteins-haptocorrin, intrinsic factor and transcobalamin-exploit slight structural differences and unique ligand receptor interactions to effect selective Cbl absorption and internalisation. We describe recent advances in the understanding of how endocytosed Cbl is transported across the lysosomal membrane and the implications of the recently solved ABCD4 structure. We detail how MMACHC and MMADHC cooperate to modify and target cytosolic Cbl to the client enzymes MTR and MMUT using ingenious modifications to an ancient nitroreductase fold, and how MTR and MMUT link with their accessory enzymes to sustainably harness the supernucleophilic potential of Cbl. Finally, we provide an outlook on how future studies may combine structural and interactome based approaches and incorporate knowledge of post-translational modifications to bring further insights.
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Affiliation(s)
- Thomas J McCorvie
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - Douglas Ferreira
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, UK
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Wyatt W Yue
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - D Sean Froese
- Division of Metabolism and Children's Research Center, University Children's Hospital Zürich, University of Zürich, Zürich, Switzerland
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Li Z, Gouda H, Pillay S, Yaw M, Ruetz M, Banerjee R. The human B 12 trafficking chaperones: CblA, ATR, CblC and CblD. Methods Enzymol 2022; 668:137-156. [PMID: 35589192 PMCID: PMC9418966 DOI: 10.1016/bs.mie.2021.12.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mammals rely on an elaborate intracellular trafficking pathway for processing and delivering vitamin B12 to two client enzymes. CblC (also known as MMACHC) is postulated to receive the cofactor as it enters the cytoplasm and converts varied B12 derivatives to a common cob(II)alamin intermediate. CblD (or MMADHC) reacts with CblC-bound cob(II)alamin forming an interprotein thiolato-cobalt coordination complex and, by a mechanism that remains to be elucidated, transfers the cofactor to methionine synthase. In the mitochondrion, CblB (also known as MMAB or adenosyltransferase) synthesizes AdoCbl from cob(II)alamin and ATP in the presence of an electron donor. CblA (or MMAA), a GTPase, gates cofactor loading from CblB to methylmalonyl-CoA mutase and off-loading of cob(II)alamin in the reverse direction. This chapter focuses on assays for measuring the activities of the four B12 chaperones CblA-D.
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Affiliation(s)
- Zhu Li
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Harsha Gouda
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Shubhadra Pillay
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Madeline Yaw
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Markus Ruetz
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Ruma Banerjee
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States
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8
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Mascarenhas R, Gouda H, Ruetz M, Banerjee R. Human B 12-dependent enzymes: Methionine synthase and Methylmalonyl-CoA mutase. Methods Enzymol 2022; 668:309-326. [PMID: 35589199 PMCID: PMC9420401 DOI: 10.1016/bs.mie.2021.12.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Humans have only two known cobalamin or B12-dependent enzymes: cytoplasmic methionine synthase and mitochondrial methylmalonyl-CoA mutase. A complex intracellular B12 trafficking pathway, comprising a multitude of chaperones, process and deliver cobalamin to the two target enzymes. Methionine synthase catalyzes the transfer of a methyl group from N5-methytetrahydrofolate to homocysteine, generating tetrahydrofolate and methionine. Cobalamin serves as an intermediate methyl group carrier and cycles between methylcobalamin and cob(I)alamin. Methylmalonyl-CoA mutase uses the 5'-deoxyadenosylcobalamin form of the cofactor and catalyzes the 1,2 rearrangement of methylmalonyl-CoA to succinyl-CoA. Two chaperones, CblA (or MMAA) and CblB (or MMAB, also known as adenosyltransferase), serve the mutase and ensure that the fidelity of the cofactor loading and unloading processes is maintained. This chapter focuses on assays for purifying and measuring the activities of methionine synthase and methylmalonyl-CoA mutase.
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Forny P, Plessl T, Frei C, Bürer C, Froese DS, Baumgartner MR. Spectrum and characterization of bi-allelic variants in MMAB causing cblB-type methylmalonic aciduria. Hum Genet 2021; 141:1253-1267. [PMID: 34796408 PMCID: PMC9262797 DOI: 10.1007/s00439-021-02398-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 11/03/2021] [Indexed: 12/31/2022]
Abstract
Pathogenic variants in MMAB cause cblB-type methylmalonic aciduria, an autosomal-recessive disorder of propionate metabolism. MMAB encodes ATP:cobalamin adenosyltransferase, using ATP and cob(I)alamin to create 5’-deoxyadenosylcobalamin (AdoCbl), the cofactor of methylmalonyl-CoA mutase (MMUT). We identified bi-allelic disease-causing variants in MMAB in 97 individuals with cblB-type methylmalonic aciduria, including 33 different and 16 novel variants. Missense changes accounted for the most frequent pathogenic alleles (p.(Arg186Trp), N = 57; p.(Arg191Trp), N = 19); while c.700C > T (p.(Arg234*)) was the most frequently identified truncating variant (N = 14). In fibroblasts from 76 affected individuals, the ratio of propionate incorporation in the presence and absence of hydroxocobalamin (PI ratio) was associated to clinical cobalamin responsiveness and later disease onset. We found p.(Arg234*) to be associated with cobalamin responsiveness in vitro, and clinically with later onset; p.(Arg186Trp) and p.(Arg191Trp) showed no clear cobalamin responsiveness and early onset. Mapping these and novel variants onto the MMAB structure revealed their potential to affect ATP and AdoCbl binding. Follow-up biochemical characterization of recombinant MMAB identified its three active sites to be equivalent for ATP binding, determined by fluorescence spectroscopy (Kd = 21 µM) and isothermal calorimetry (Kd = 14 µM), but function as two non-equivalent AdoCbl binding sites (Kd1 = 0.55 μM; Kd2 = 8.4 μM). Ejection of AdoCbl was activated by ATP (Ka = 24 µM), which was sensitized by the presence of MMUT (Ka = 13 µM). This study expands the landscape of pathogenic MMAB variants, provides association of in vitro and clinical responsiveness, and facilitates insight into MMAB function, enabling better disease understanding.
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Affiliation(s)
- Patrick Forny
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, University of Zurich, 8032, Zurich, Switzerland
| | - Tanja Plessl
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, University of Zurich, 8032, Zurich, Switzerland
| | - Caroline Frei
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, University of Zurich, 8032, Zurich, Switzerland
| | - Celine Bürer
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, University of Zurich, 8032, Zurich, Switzerland
| | - D Sean Froese
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, University of Zurich, 8032, Zurich, Switzerland.
| | - Matthias R Baumgartner
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, University of Zurich, 8032, Zurich, Switzerland.
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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] [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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11
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Mobile loop dynamics in adenosyltransferase control binding and reactivity of coenzyme B 12. Proc Natl Acad Sci U S A 2020; 117:30412-30422. [PMID: 33199623 DOI: 10.1073/pnas.2007332117] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Cobalamin is a complex organometallic cofactor that is processed and targeted via a network of chaperones to its dependent enzymes. AdoCbl (5'-deoxyadenosylcobalamin) is synthesized from cob(II)alamin in a reductive adenosylation reaction catalyzed by adenosyltransferase (ATR), which also serves as an escort, delivering AdoCbl to methylmalonyl-CoA mutase (MCM). The mechanism by which ATR signals that its cofactor cargo is ready (AdoCbl) or not [cob(II)alamin] for transfer to MCM, is not known. In this study, we have obtained crystallographic snapshots that reveal ligand-induced ordering of the N terminus of Mycobacterium tuberculosis ATR, which organizes a dynamic cobalamin binding site and exerts exquisite control over coordination geometry, reactivity, and solvent accessibility. Cob(II)alamin binds with its dimethylbenzimidazole tail splayed into a side pocket and its corrin ring buried. The cosubstrate, ATP, enforces a four-coordinate cob(II)alamin geometry, facilitating the unfavorable reduction to cob(I)alamin. The binding mode for AdoCbl is notably different from that of cob(II)alamin, with the dimethylbenzimidazole tail tucked under the corrin ring, displacing the N terminus of ATR, which is disordered. In this solvent-exposed conformation, AdoCbl undergoes facile transfer to MCM. The importance of the tail in cofactor handover from ATR to MCM is revealed by the failure of 5'-deoxyadenosylcobinamide, lacking the tail, to transfer. In the absence of MCM, ATR induces a sacrificial cobalt-carbon bond homolysis reaction in an unusual reversal of the heterolytic chemistry that was deployed to make the same bond. The data support an important role for the dimethylbenzimidazole tail in moving the cobalamin cofactor between active sites.
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Costa FG, Greenhalgh ED, Brunold TC, Escalante-Semerena JC. Mutational and Functional Analyses of Substrate Binding and Catalysis of the Listeria monocytogenes EutT ATP:Co(I)rrinoid Adenosyltransferase. Biochemistry 2020; 59:1124-1136. [PMID: 32125848 DOI: 10.1021/acs.biochem.0c00078] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
ATP:Co(I)rrinoid adenosyltransferases (ACATs) catalyze the transfer of the adenosyl moiety from co-substrate ATP to a corrinoid substrate. ACATs are grouped into three families, namely, CobA, PduO, and EutT. The EutT family of enzymes is further divided into two classes, depending on whether they require a divalent metal ion for activity (class I and class II). To date, a structure has not been elucidated for either class of the EutT family of ACATs. In this work, results of bioinformatics analyses revealed several conserved residues between the C-terminus of EutT homologues and the structurally characterized Lactobacillus reuteri PduO (LrPduO) homologue. In LrPduO, these residues are associated with ATP binding and formation of an intersubunit salt bridge. These residues were substituted, and in vivo and in vitro data support the conclusion that the equivalent residues in the metal-free (i.e., class II) Listeria monocytogenes EutT (LmEutT) enzyme affect ATP binding. Results of in vivo and in vitro analyses of LmEutT variants with substitutions at phenylalanine and tryptophan residues revealed that replacement of the phenylalanine residue at position 72 affected access to the substrate-binding site and replacement of a tryptophan residue at position 238 affected binding of the Cbl substrate to the active site. Unlike the PduO family of ACATs, a single phenylalanine residue is not responsible for displacement of the α-ligand. Together, these data suggest that while EutT enzymes share a conserved ATP-binding motif and an intersubunit salt bridge with PduO family ACATs, class II EutT family ACATs utilize an unidentified mechanism for Cbl lower-ligand displacement and reduction that is different from that of PduO and CobA family ACATs.
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Affiliation(s)
- Flavia G Costa
- Department of Microbiology, University of Georgia, Athens, Georgia 30602, United States
| | - Elizabeth D Greenhalgh
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
| | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
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Ruetz M, Campanello GC, McDevitt L, Yokom AL, Yadav PK, Watkins D, Rosenblatt DS, Ohi MD, Southworth DR, Banerjee R. Allosteric Regulation of Oligomerization by a B 12 Trafficking G-Protein Is Corrupted in Methylmalonic Aciduria. Cell Chem Biol 2019; 26:960-969.e4. [PMID: 31056463 DOI: 10.1016/j.chembiol.2019.03.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 03/07/2019] [Accepted: 03/25/2019] [Indexed: 10/26/2022]
Abstract
Allosteric regulation of methylmalonyl-CoA mutase (MCM) by the G-protein chaperone CblA is transduced via three "switch" elements that gate the movement of the B12 cofactor to and from MCM. Mutations in CblA and MCM cause hereditary methylmalonic aciduria. Unlike the bacterial orthologs used previously to model disease-causing mutations, human MCM and CblA exhibit a complex pattern of regulation that involves interconverting oligomers, which are differentially sensitive to the presence of GTP versus GDP. Patient mutations in the switch III region of CblA perturb the nucleotide-sensitive distribution of the oligomeric complexes with MCM, leading to loss of regulated movement of B12 to and/or from MCM and explain the molecular mechanism of the resulting disease.
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Affiliation(s)
- Markus Ruetz
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI, USA
| | - Gregory C Campanello
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI, USA
| | - Liam McDevitt
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI, USA
| | - Adam L Yokom
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Pramod K Yadav
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - David Watkins
- Department of Human Genetics, McGill University, Montreal, QC H3A 1B1, Canada
| | - David S Rosenblatt
- Department of Human Genetics, McGill University, Montreal, QC H3A 1B1, Canada
| | - Melanie D Ohi
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Daniel R Southworth
- Department of Biochemistry and Biophysics, Institute for Neurodegenerative Diseases, University of California-San Francisco, San Francisco, CA 94158, USA
| | - Ruma Banerjee
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI, USA.
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Campanello GC, Lofgren M, Yokom AL, Southworth DR, Banerjee R. Switch I-dependent allosteric signaling in a G-protein chaperone-B 12 enzyme complex. J Biol Chem 2017; 292:17617-17625. [PMID: 28882898 DOI: 10.1074/jbc.m117.786095] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 08/14/2017] [Indexed: 11/06/2022] Open
Abstract
G-proteins regulate various processes ranging from DNA replication and protein synthesis to cytoskeletal dynamics and cofactor assimilation and serve as models for uncovering strategies deployed for allosteric signal transduction. MeaB is a multifunctional G-protein chaperone, which gates loading of the active 5'-deoxyadenosylcobalamin cofactor onto methylmalonyl-CoA mutase (MCM) and precludes loading of inactive cofactor forms. MeaB also safeguards MCM, which uses radical chemistry, against inactivation and rescues MCM inactivated during catalytic turnover by using the GTP-binding energy to offload inactive cofactor. The conserved switch I and II signaling motifs used by G-proteins are predicted to mediate allosteric regulation in response to nucleotide binding and hydrolysis in MeaB. Herein, we targeted conserved residues in the MeaB switch I motif to interrogate the function of this loop. Unexpectedly, the switch I mutations had only modest effects on GTP binding and on GTPase activity and did not perturb stability of the MCM-MeaB complex. However, these mutations disrupted multiple MeaB chaperone functions, including cofactor editing, loading, and offloading. Hence, although residues in the switch I motif are not essential for catalysis, they are important for allosteric regulation. Furthermore, single-particle EM analysis revealed, for the first time, the overall architecture of the MCM-MeaB complex, which exhibits a 2:1 stoichiometry. These EM studies also demonstrate that the complex exhibits considerable conformational flexibility. In conclusion, the switch I element does not significantly stabilize the MCM-MeaB complex or influence the affinity of MeaB for GTP but is required for transducing signals between MeaB and MCM.
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Affiliation(s)
- Gregory C Campanello
- From the Departments of Biological Chemistry, University of Michigan Medical Center, and
| | - Michael Lofgren
- From the Departments of Biological Chemistry, University of Michigan Medical Center, and
| | - Adam L Yokom
- From the Departments of Biological Chemistry, University of Michigan Medical Center, and.,the Department of Biological Chemistry and.,the Graduate Program in Chemical Biology, Life Sciences Institute, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600
| | - Daniel R Southworth
- From the Departments of Biological Chemistry, University of Michigan Medical Center, and.,the Department of Biological Chemistry and
| | - Ruma Banerjee
- From the Departments of Biological Chemistry, University of Michigan Medical Center, and
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15
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The cause of multiple sclerosis is autoimmune attack of adenosyltransferase thereby limiting adenosylcobalamin production. Med Hypotheses 2017; 109:29-37. [PMID: 29150289 DOI: 10.1016/j.mehy.2017.08.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 06/20/2017] [Accepted: 08/06/2017] [Indexed: 01/17/2023]
Abstract
The pathogenesis of multiple sclerosis (MS) begins with an infection by a bacterium from the class of bacteria that produce and utilize adenosylcobalamin (AdoCbl) and possess an adenosyl transferase enzyme (ATR); these bacteria are the exogenous antigens that cause MS. Human ATR is homologous to bacterial ATR and B cells produce anti-ATR antibodies as an autoimmune response thereby reducing the concentration of ATR and thus limiting production of AdoCbl, one of the two bioactive forms of vitamin B12. The next step in MS pathogenesis is a period of subclinical AdoCbl deficiency over a period of many years resulting in production of odd-carbon-number fatty acids that are incorporated into myelin rendering it antigenic. The next step in MS pathogenesis is breach of the blood brain barrier thereby introducing leukocytes into the brain's blood supply resulting in T cell attack of antigenic myelin. All epidemiological clusters are regions wherein the major agricultural products are legumes that produce a high percentage of odd-carbon-number fatty acids and contain symbiotic rhizobia type bacteria in root nodules and in the soil. This novel etiological hypothesis is called "multiple sclerosis due to adenosylcobalamin deficiency" (MS-AdoCbl). Creation of realistic animal models based on the MS-AdoCbl hypothesis is presented. Methods for testing predictions made by the MS-AdoCbl hypothesis are described.
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16
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Li Z, Kitanishi K, Twahir UT, Cracan V, Chapman D, Warncke K, Banerjee R. Cofactor Editing by the G-protein Metallochaperone Domain Regulates the Radical B 12 Enzyme IcmF. J Biol Chem 2017; 292:3977-3987. [PMID: 28130442 DOI: 10.1074/jbc.m117.775957] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Indexed: 11/06/2022] Open
Abstract
IcmF is a 5'-deoxyadenosylcobalamin (AdoCbl)-dependent enzyme that catalyzes the carbon skeleton rearrangement of isobutyryl-CoA to butyryl-CoA. It is a bifunctional protein resulting from the fusion of a G-protein chaperone with GTPase activity and the cofactor- and substrate-binding mutase domains with isomerase activity. IcmF is prone to inactivation during catalytic turnover, thus setting up its dependence on a cofactor repair system. Herein, we demonstrate that the GTPase activity of IcmF powers the ejection of the inactive cob(II)alamin cofactor and requires the presence of an acceptor protein, adenosyltransferase, for receiving it. Adenosyltransferase in turn converts cob(II)alamin to AdoCbl in the presence of ATP and a reductant. The repaired cofactor is then reloaded onto IcmF in a GTPase-gated step. The mechanistic details of cofactor loading and offloading from the AdoCbl-dependent IcmF are distinct from those of the better characterized and homologous methylmalonyl-CoA mutase/G-protein chaperone system.
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Affiliation(s)
- Zhu Li
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600 and
| | - Kenichi Kitanishi
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600 and
| | - Umar T Twahir
- the Department of Physics, Emory University, Atlanta, Georgia 30322-2430
| | - Valentin Cracan
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600 and
| | - Derrell Chapman
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600 and
| | - Kurt Warncke
- the Department of Physics, Emory University, Atlanta, Georgia 30322-2430
| | - Ruma Banerjee
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600 and
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17
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Barile M, Giancaspero TA, Leone P, Galluccio M, Indiveri C. Riboflavin transport and metabolism in humans. J Inherit Metab Dis 2016; 39:545-57. [PMID: 27271694 DOI: 10.1007/s10545-016-9950-0] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 05/12/2016] [Accepted: 05/19/2016] [Indexed: 12/17/2022]
Abstract
Recent studies elucidated how riboflavin transporters and FAD forming enzymes work in humans and create a coordinated flavin network ensuring the maintenance of cellular flavoproteome. Alteration of this network may be causative of severe metabolic disorders such as multiple acyl-CoA dehydrogenase deficiency (MADD) or Brown-Vialetto-van Laere syndrome. A crucial step in the maintenance of FAD homeostasis is riboflavin uptake by plasma and mitochondrial membranes. Therefore, studies on recently identified human plasma membrane riboflavin transporters are presented, together with those in which still unidentified mitochondrial riboflavin transporter(s) have been described. A main goal of future research is to fill the gaps still existing as for some transcriptional, functional and structural details of human FAD synthases (FADS) encoded by FLAD1 gene, a novel "redox sensing" enzyme. In the frame of the hypothesis that FADS, acting as a "FAD chaperone", could play a crucial role in the biogenesis of mitochondrial flavo-proteome, several basic functional aspects of flavin cofactor delivery to cognate apo-flavoenzyme are also briefly dealt with. The establishment of model organisms performing altered FAD homeostasis will improve the molecular description of human pathologies. The molecular and functional studies of transporters and enzymes herereported, provide guidelines for improving therapies which may have beneficial effects on the altered metabolism.
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Affiliation(s)
- Maria Barile
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari "Aldo Moro", via Orabona 4, I-70126, Bari, Italy.
| | - Teresa Anna Giancaspero
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari "Aldo Moro", via Orabona 4, I-70126, Bari, Italy
| | - Piero Leone
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari "Aldo Moro", via Orabona 4, I-70126, Bari, Italy
| | - Michele Galluccio
- Dipartimento DiBEST (Biologia, Ecologia, Scienze della Terra), Unità di Biochimica e Biotecnologie Molecolari, Università della Calabria, via Bucci 4c, I-87036, Arcavacata di Rende, Italy
| | - Cesare Indiveri
- Dipartimento DiBEST (Biologia, Ecologia, Scienze della Terra), Unità di Biochimica e Biotecnologie Molecolari, Università della Calabria, via Bucci 4c, I-87036, Arcavacata di Rende, Italy
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18
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Giancaspero TA, Colella M, Brizio C, Difonzo G, Fiorino GM, Leone P, Brandsch R, Bonomi F, Iametti S, Barile M. Remaining challenges in cellular flavin cofactor homeostasis and flavoprotein biogenesis. Front Chem 2015; 3:30. [PMID: 25954742 PMCID: PMC4406087 DOI: 10.3389/fchem.2015.00030] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 04/05/2015] [Indexed: 12/27/2022] Open
Abstract
The primary role of the water-soluble vitamin B2 (riboflavin) in cell biology is connected with its conversion into FMN and FAD, the cofactors of a large number of dehydrogenases, oxidases and reductases involved in a broad spectrum of biological activities, among which energetic metabolism and chromatin remodeling. Subcellular localisation of FAD synthase (EC 2.7.7.2, FADS), the second enzyme in the FAD forming pathway, is addressed here in HepG2 cells by confocal microscopy, in the frame of its relationships with kinetics of FAD synthesis and delivery to client apo-flavoproteins. FAD synthesis catalyzed by recombinant isoform 2 of FADS occurs via an ordered bi-bi mechanism in which ATP binds prior to FMN, and pyrophosphate is released before FAD. Spectrophotometric continuous assays of the reconstitution rate of apo-D-aminoacid oxidase with its cofactor, allowed us to propose that besides its FAD synthesizing activity, hFADS is able to operate as a FAD “chaperone.” The physical interaction between FAD forming enzyme and its clients was further confirmed by dot blot and immunoprecipitation experiments carried out testing as a client either a nuclear lysine-specific demethylase 1 (LSD1) or a mitochondrial dimethylglycine dehydrogenase (Me2GlyDH, EC 1.5.8.4). Both enzymes carry out similar reactions of oxidative demethylation, in which tetrahydrofolate is converted into 5,10-methylene-tetrahydrofolate. A direct transfer of the cofactor from hFADS2 to apo-dimethyl glycine dehydrogenase was also demonstrated. Thus, FAD synthesis and delivery to these enzymes are crucial processes for bioenergetics and nutri-epigenetics of liver cells.
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Affiliation(s)
- Teresa A Giancaspero
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari Aldo Moro Bari, Italy
| | - Matilde Colella
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari Aldo Moro Bari, Italy
| | - Carmen Brizio
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari Aldo Moro Bari, Italy
| | - Graziana Difonzo
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari Aldo Moro Bari, Italy
| | - Giuseppina M Fiorino
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari Aldo Moro Bari, Italy
| | - Piero Leone
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari Aldo Moro Bari, Italy
| | - Roderich Brandsch
- Institut für Biochemie und Molekularbiologie, Universität Freiburg Freiburg, Germany
| | - Francesco Bonomi
- Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente, Università degli Studi di Milano Milano, Italy
| | - Stefania Iametti
- Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente, Università degli Studi di Milano Milano, Italy
| | - Maria Barile
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari Aldo Moro Bari, Italy ; Dipartimento di Scienze della Vita, Istituto di Biomembrane e Bioenergetica, CNR Bari, Italy
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19
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Pallares IG, Moore TC, Escalante-Semerena JC, Brunold TC. Spectroscopic studies of the Salmonella enterica adenosyltransferase enzyme SeCobA: molecular-level insight into the mechanism of substrate Cob(II)alamin activation. Biochemistry 2014; 53:7969-82. [PMID: 25423616 PMCID: PMC4278676 DOI: 10.1021/bi5011877] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
CobA from Salmonella enterica (SeCobA) is a member of the family of ATP:Co(I)rrinoid adenosyltransferase (ACAT) enzymes that participate in the biosynthesis of adenosylcobalamin by catalyzing the transfer of the adenosyl group from an ATP molecule to a reactive Co(I)rrinoid species transiently generated in the enzyme active site. This reaction is thermodynamically challenging, as the reduction potential of the Co(II)rrinoid precursor in solution is far more negative than that of available reducing agents in the cell (e.g., flavodoxin), precluding nonenzymic reduction to the Co(I) oxidation state. However, in the active sites of ACATs, the Co(II)/Co(I) redox potential is increased by >250 mV via the formation of a unique four-coordinate (4c) Co(II)rrinoid species. In the case of the SeCobA ACAT, crystallographic and kinetic studies have revealed that the phenylalanine 91 (F91) and tryptophan 93 (W93) residues are critical for in vivo activity, presumably by blocking access to the lower axial ligand site of the Co(II)rrinoid substrate. To further assess the importance of the F91 and W93 residues with respect to enzymatic function, we have characterized various SeCobA active-site variants using electronic absorption, magnetic circular dichroism, and electron paramagnetic resonance spectroscopies. Our data provide unprecedented insight into the mechanism by which SeCobA converts the Co(II)rrinoid substrate to 4c species, with the hydrophobicity, size, and ability to participate in offset π-stacking interactions of key active-site residues all being critical for activity. The structural changes that occur upon Co(II)rrinoid binding also appear to be crucial for properly orienting the transiently generated Co(I) "supernucleophile" for rapid reaction with cosubstrate ATP.
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Affiliation(s)
- Ivan G Pallares
- Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
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20
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A switch III motif relays signaling between a B12 enzyme and its G-protein chaperone. Nat Chem Biol 2013; 9:535-9. [PMID: 23873214 PMCID: PMC3752380 DOI: 10.1038/nchembio.1298] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Accepted: 06/24/2013] [Indexed: 01/17/2023]
Abstract
Fidelity during cofactor assembly is essential for the proper functioning of metalloenzymes and is ensured by specific chaperones. MeaB, a G-protein chaperone for the coenzyme B12-dependent radical enzyme, methylmalonyl-CoA mutase (MCM), utilizes the energy of GTP binding and/or hydrolysis to regulate cofactor loading into MCM, protect MCM from inactivation, and rescue MCM inactivated during turnover. Typically, G-proteins signal to client proteins using the conformationally mobile switch I and II loops. Crystallographic snapshots of MeaB reported herein reveal a novel switch III element, which exhibits substantial conformational plasticity. Using alanine-scanning mutagenesis, we demonstrate that the switch III motif is critical for bidirectional signal transmission of the GTPase activating protein activity of MCM and the chaperone functions of MeaB in the MeaB:MCM complex. Mutations in the switch III loop identified in patients corrupt this inter-protein communication and lead to methylmalonic aciduria, an inborn error of metabolism.
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21
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Dassanayake RS, Cabelli DE, Brasch NE. Pulse radiolysis studies on the reaction of the reduced vitamin B₁₂ complex Cob(II)alamin with superoxide. Chembiochem 2013; 14:1081-3. [PMID: 23671003 PMCID: PMC3737425 DOI: 10.1002/cbic.201300229] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Indexed: 01/25/2023]
Abstract
O₂.- scavenger: The rate constant for the rapid reaction of the ROS superoxide with the reduced vitamin B₁₂ radical complex cob(II)alamin was directly determined to be 3.8×10(8) M⁻¹ s⁻¹. This rate was independent of pH over the range 5.5-8.7. These results have implications for studying the use of B₁₂ supplements to combat diseases associated with oxidative stress.
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Affiliation(s)
- Rohan S. Dassanayake
- Department of Chemistry & Biochemistry and School of Biomedical Sciences Kent State University Kent, OH 44242(USA)
| | - Diane E. Cabelli
- Department of Chemistry & Biochemistry and School of Biomedical Sciences Kent State University Kent, OH 44242(USA)
- Department of Chemistry Brookhaven National Laboratory Upton, NY 11973(USA)
| | - Nicola E. Brasch
- Department of Chemistry & Biochemistry and School of Biomedical Sciences Kent State University Kent, OH 44242(USA)
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22
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Gherasim C, Lofgren M, Banerjee R. Navigating the B(12) road: assimilation, delivery, and disorders of cobalamin. J Biol Chem 2013; 288:13186-93. [PMID: 23539619 DOI: 10.1074/jbc.r113.458810] [Citation(s) in RCA: 134] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The reactivity of the cobalt-carbon bond in cobalamins is the key to their chemical versatility, supporting both methyl transfer and isomerization reactions. During evolution of higher eukaryotes that utilize vitamin B12, the high reactivity of the cofactor coupled with its low abundance pressured development of an efficient system for uptake, assimilation, and delivery of the cofactor to client B12-dependent enzymes. Although most proteins suspected to be involved in B12 trafficking were discovered by 2009, the recent identification of a new protein reveals that the quest for elucidating the intracellular B12 highway is still far from complete. Herein, we review the biochemistry of cobalamin trafficking.
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Affiliation(s)
- Carmen Gherasim
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI 48109-0600, USA
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23
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Plymale NT, Dassanayake RS, Hassanin HA, Brasch NE. Kinetic and Mechanistic Studies on the Reactions of the Reduced Vitamin B12 Complex Cob(I)alamin with Nitrite and Nitrate. Eur J Inorg Chem 2011. [DOI: 10.1002/ejic.201100992] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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24
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Torchetti EM, Bonomi F, Galluccio M, Gianazza E, Giancaspero TA, Iametti S, Indiveri C, Barile M. Human FAD synthase (isoform 2): a component of the machinery that delivers FAD to apo-flavoproteins. FEBS J 2011; 278:4434-49. [PMID: 21951714 DOI: 10.1111/j.1742-4658.2011.08368.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A soluble form of human FAD synthase (isoform 2; hFADS2) was produced and purified to homogeneity as a recombinant His-tagged protein. The enzyme binds 1 mole of the FAD product very tightly, although noncovalently. Complete release of FAD from the 'as isolated' protein requires extensive denaturation. A 75 : 25 mixture of apo/holoprotein could be prepared by treatment with mild chaotropes, allowing estimatation of the contribution made by bound FAD to the protein stability and evaluatation of whether structural rearrangements may be required for FAD release. Under turnover conditions, the enzyme catalyzes FAD assembly from ATP and FMN and, at a much lower rate, the pyrophosphorolytic hydrolysis of FAD. Several mechanistic features of both reactions were investigated in detail, along with their dependence on environmental conditions (pH, temperature, dependence on metals). Our data indicate that FAD release may represent the rate-limiting step of the whole catalytic cycle and that the process leading to FAD synthesis, and delivery to client apoproteins may be tightly controlled.
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Affiliation(s)
- Enza M Torchetti
- Dipartimento di Biochimica e Biologia Molecolare E. Quagliariello (DBBM), Università degli Studi di Bari, Bari, Italy
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25
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Mukherjee R, Brasch NE. Kinetic studies on the reaction between cob(I)alamin and peroxynitrite: rapid oxidation of cob(I)alamin to cob(II)alamin by peroxynitrous acid. Chemistry 2011; 17:11723-7. [PMID: 21922587 DOI: 10.1002/chem.201102267] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Indexed: 11/06/2022]
Affiliation(s)
- Riya Mukherjee
- Department of Chemistry & Biochemistry and School of Biomedical Sciences, Kent State University, Kent, OH 44242, USA
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26
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Lofgren M, Banerjee R. Loss of allostery and coenzyme B12 delivery by a pathogenic mutation in adenosyltransferase. Biochemistry 2011; 50:5790-8. [PMID: 21604717 DOI: 10.1021/bi2006306] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
ATP-dependent cob(I)alamin adenosyltransferase (ATR) is a bifunctional protein: an enzyme that catalyzes the adenosylation of cob(I)alamin and an escort that delivers the product, adenosylcobalamin (AdoCbl or coenzyme B(12)), to methylmalonyl-CoA mutase (MCM), resulting in holoenzyme formation. Failure to assemble holo-MCM leads to methylmalonic aciduria. We have previously demonstrated that only 2 equiv of AdoCbl bind per homotrimer of ATR and that binding of ATP to the vacant active site triggers ejection of 1 equiv of AdoCbl from an adjacent site. In this study, we have mimicked in the Methylobacterium extorquens ATR, a C-terminal truncation mutation, D180X, described in a patient with methylmalonic aciduria, and characterized the associated biochemical penalties. We demonstrate that while k(cat) and K(M)(Cob(I)) for D180X ATR are only modestly decreased (by 3- and 2-fold, respectively), affinity for the product, AdoCbl, is significantly diminished (400-fold), and the negative cooperativity associated with its binding is lost. We also demonstrate that the D180X mutation corrupts ATP-dependent cofactor ejection, which leads to transfer of AdoCbl from wild-type ATR to MCM. These results suggest that the pathogenicity of the corresponding human truncation mutant results from its inability to sequester AdoCbl for direct transfer to MCM. Instead, cofactor release into solution is predicted to reduce the capacity for holo-MCM formation, leading to disease.
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Affiliation(s)
- Michael Lofgren
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600, USA
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27
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Peng J, Tang KC, McLoughlin K, Yang Y, Forgach D, Sension RJ. Ultrafast Excited-State Dynamics and Photolysis in Base-Off B12 Coenzymes and Analogues: Absence of the trans-Nitrogenous Ligand Opens a Channel for Rapid Nonradiative Decay. J Phys Chem B 2010; 114:12398-405. [DOI: 10.1021/jp104641u] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Jian Peng
- Department of Chemistry and Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1055
| | - Kuo-Chun Tang
- Department of Chemistry and Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1055
| | - Kaitlin McLoughlin
- Department of Chemistry and Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1055
| | - Yang Yang
- Department of Chemistry and Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1055
| | - Danika Forgach
- Department of Chemistry and Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1055
| | - Roseanne J. Sension
- Department of Chemistry and Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1055
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28
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Mera PE, Escalante-Semerena JC. Multiple roles of ATP:cob(I)alamin adenosyltransferases in the conversion of B12 to coenzyme B12. Appl Microbiol Biotechnol 2010; 88:41-8. [PMID: 20677021 DOI: 10.1007/s00253-010-2773-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 07/06/2010] [Accepted: 07/08/2010] [Indexed: 10/19/2022]
Abstract
Our mechanistic understanding of the conversion of vitamin B(12) into coenzyme B(12) (a.k.a. adenosylcobalamin, AdoCbl) has been substantially advanced in recent years. Insights into the multiple roles played by ATP:cob(I)alamin adenosyltransferase (ACA) enzymes have emerged through the crystallographic, spectroscopic, biochemical, and mutational analyses of wild-type and variant proteins. ACA enzymes circumvent the thermodynamic barrier posed by the very low redox potential associated with the reduction of cob(II)alamin to cob(I)alamin by generating a unique four-coordinate cob(II)alamin intermediate that is readily converted to cob(I)alamin by physiological reductants. ACA enzymes not only synthesize AdoCbl but also they deliver it to the enzymes that use it, and in some cases, enzymes in which its function is needed to maintain the fidelity of the AdoCbl delivery process have been identified. Advances in our understanding of ACA enzyme function have provided valuable insights into the role of specific residues, and into why substitutions of these residues have profound negative effects on human health. From an applied science standpoint, a better understanding of the adenosylation reaction may lead to more efficient ways of synthesizing AdoCbl.
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Affiliation(s)
- Paola E Mera
- Department of Developmental Biology, Stanford University, 279 Campus Drive, Stanford, CA 94305, USA
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29
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A G-protein editor gates coenzyme B12 loading and is corrupted in methylmalonic aciduria. Proc Natl Acad Sci U S A 2009; 106:21567-72. [PMID: 19955418 DOI: 10.1073/pnas.0908106106] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The mechanism by which docking fidelity is achieved for the multitude of cofactor-dependent enzymes is poorly understood. In this study, we demonstrate that delivery of coenzyme B(12) or 5'-deoxyadenosylcobalamin by adenosyltransferase to methylmalonyl-CoA mutase is gated by a small G protein, MeaB. While the GTP-binding energy is needed for the editing function; that is, to discriminate between active and inactive cofactor forms, the chemical energy of GTP hydrolysis is required for gating cofactor transfer. The G protein chaperone also exerts its editing function during turnover by using the binding energy of GTP to elicit release of inactive cofactor that is occasionally formed during the catalytic cycle of MCM. The physiological relevance of this mechanism is demonstrated by a patient mutation in methylmalonyl-CoA mutase that does not impair the activity of this enzyme per se but corrupts both the fidelity of the cofactor-loading process and the ejection of inactive cofactor that forms occasionally during catalysis. Consequently, cofactor in the incorrect oxidation state gains access to the mutase active site and is not released if generated during catalysis, leading, respectively, to assembly and accumulation of inactive enzyme and resulting in methylmalonic aciduria.
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Banerjee R, Gherasim C, Padovani D. The tinker, tailor, soldier in intracellular B12 trafficking. Curr Opin Chem Biol 2009; 13:484-91. [PMID: 19665918 DOI: 10.1016/j.cbpa.2009.07.007] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 07/02/2009] [Accepted: 07/09/2009] [Indexed: 11/19/2022]
Abstract
The recognition of eight discrete genetic complementation groups among patients with inherited cobalamin disorders provided early insights into the complexity of a cofactor-processing pathway that supports only two known B(12)-dependent enzymes in mammals. With the identification of all eight genes now completed, biochemical interrogations of their functions have started and are providing novel insights into a trafficking pathway involving porters that tinker with and tailor the active cofactor forms and editors that ensure the fidelity of the cofactor loading process. The principles of sequestration and escorted delivery of a rare and reactive organometallic cofactor that are emerging from studies on B(12) might be of general relevance to other cofactor trafficking pathways.
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Affiliation(s)
- Ruma Banerjee
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI 48109-5606, USA.
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