1
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Song WS, Kim JH, Namgung B, Cho HY, Shin H, Oh HB, Ha NC, Yoon SI. Complementary hydrophobic interaction of the redox enzyme maturation protein NarJ with the signal peptide of the respiratory nitrate reductase NarG. Int J Biol Macromol 2024; 262:129620. [PMID: 38262549 DOI: 10.1016/j.ijbiomac.2024.129620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 01/08/2024] [Accepted: 01/18/2024] [Indexed: 01/25/2024]
Abstract
In bacteria, NarJ plays an essential role as a redox enzyme maturation protein in the assembly of the nitrate reductase NarGHI by interacting with the N-terminal signal peptide of NarG to facilitate cofactor incorporation into NarG. The purpose of our research was to elucidate the exact mechanism of NarG signal peptide recognition by NarJ. We determined the structures of NarJ alone and in complex with the signal peptide of NarG via X-ray crystallography and verified the NarJ-NarG interaction through mutational, binding, and molecular dynamics simulation studies. NarJ adopts a curved α-helix bundle structure with a U-shaped hydrophobic groove on its concave side. This groove accommodates the signal peptide of NarG via a dual binding mode in which the left and right parts of the NarJ groove each interact with two consecutive hydrophobic residues from the N- and C-terminal regions of the NarG signal peptide, respectively, through shape and chemical complementarity. This binding is accompanied by unwinding of the helical structure of the NarG signal peptide and by stabilization of the NarG-binding loop of NarJ. We conclude that NarJ recognizes the NarG signal peptide through a complementary hydrophobic interaction mechanism that mediates a structural rearrangement.
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Affiliation(s)
- Wan Seok Song
- Institute of Bioscience and Biotechnology, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Jee-Hyeon Kim
- Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Byeol Namgung
- Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Hye Yeon Cho
- Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Hyunwoo Shin
- Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Sciences, College of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Han Byeol Oh
- Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Nam-Chul Ha
- Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Sciences, College of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Sung-Il Yoon
- Institute of Bioscience and Biotechnology, Kangwon National University, Chuncheon 24341, Republic of Korea; Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon 24341, Republic of Korea.
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2
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Magalon A. History of Maturation of Prokaryotic Molybdoenzymes-A Personal View. Molecules 2023; 28:7195. [PMID: 37894674 PMCID: PMC10609526 DOI: 10.3390/molecules28207195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 10/11/2023] [Accepted: 10/17/2023] [Indexed: 10/29/2023] Open
Abstract
In prokaryotes, the role of Mo/W enzymes in physiology and bioenergetics is widely recognized. It is worth noting that the most diverse family of Mo/W enzymes is exclusive to prokaryotes, with the probable existence of several of them from the earliest forms of life on Earth. The structural organization of these enzymes, which often include additional redox centers, is as diverse as ever, as is their cellular localization. The most notable observation is the involvement of dedicated chaperones assisting with the assembly and acquisition of the metal centers, including Mo/W-bisPGD, one of the largest organic cofactors in nature. This review seeks to provide a new understanding and a unified model of Mo/W enzyme maturation.
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Affiliation(s)
- Axel Magalon
- Aix Marseille Université, CNRS, Laboratoire de Chimie Bactérienne (UMR7283), IMM, IM2B, 13402 Marseille, France
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3
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Bageshwar UK, DattaGupta A, Musser SM. Influence of the TorD signal peptide chaperone on Tat-dependent protein translocation. PLoS One 2021; 16:e0256715. [PMID: 34499687 PMCID: PMC8428690 DOI: 10.1371/journal.pone.0256715] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 07/28/2021] [Indexed: 11/18/2022] Open
Abstract
The twin-arginine translocation (Tat) pathway transports folded proteins across energetic membranes. Numerous Tat substrates contain co-factors that are inserted before transport with the assistance of redox enzyme maturation proteins (REMPs), which bind to the signal peptide of precursor proteins. How signal peptides are transferred from a REMP to a binding site on the Tat receptor complex remains unknown. Since the signal peptide mediates both interactions, possibilities include: i) a coordinated hand-off mechanism; or ii) a diffusional search after REMP dissociation. We investigated the binding interaction between substrates containing the TorA signal peptide (spTorA) and its cognate REMP, TorD, and the effect of TorD on the in vitro transport of such substrates. We found that Escherichia coli TorD is predominantly a monomer at low micromolar concentrations (dimerization KD > 50 μM), and this monomer binds reversibly to spTorA (KD ≈ 1 μM). While TorD binds to membranes (KD ≈ 100 nM), it has no apparent affinity for Tat translocons and it inhibits binding of a precursor substrate to the membrane. TorD has a minimal effect on substrate transport by the Tat system, being mildly inhibitory at high concentrations. These data are consistent with a model in which the REMP-bound signal peptide is shielded from recognition by the Tat translocon, and spontaneous dissociation of the REMP allows the substrate to engage the Tat machinery. Thus, the REMP does not assist with targeting to the Tat translocon, but rather temporarily shields the signal peptide.
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Affiliation(s)
- Umesh K. Bageshwar
- Department of Molecular and Cellular Medicine, Texas A&M University, College of Medicine, The Texas A&M Health Science Center, TX, United States of America
| | - Antara DattaGupta
- Department of Molecular and Cellular Medicine, Texas A&M University, College of Medicine, The Texas A&M Health Science Center, TX, United States of America
| | - Siegfried M. Musser
- Department of Molecular and Cellular Medicine, Texas A&M University, College of Medicine, The Texas A&M Health Science Center, TX, United States of America
- * E-mail:
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4
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Ghosh D, Boral D, Vankudoth KR, Ramasamy S. Analysis of haloarchaeal twin-arginine translocase pathway reveals the diversity of the machineries. Heliyon 2019; 5:e01587. [PMID: 31193317 PMCID: PMC6525301 DOI: 10.1016/j.heliyon.2019.e01587] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 03/23/2019] [Accepted: 04/24/2019] [Indexed: 01/10/2023] Open
Abstract
The twin-arginine translocase (Tat) pathway transports folded proteins across the plasma membrane and plays a critical role in protein transport in haloarchaea. Computational analysis and previous experimental evidence suggested that the Tat pathway transports almost the entire secretome in haloarchaea. The TatC, receptor component of this pathway shows greater variation in membrane topology in haloarchaea than in other organisms. The presence of a unique fourteen-transmembrane TatC homolog (TatCt) in haloarchaea, over and above the expected TatC topological variants, indicates a strong correlation between the additional homologs and the large number of substrates transported via the haloarchaeal Tat pathway. Various combinations of TatC homologs with different topologies—TatCo, TatCt, TatCn, and TatCx have been observed in haloarchaea. In this report, on the basis of these combinations we have segregated all haloarchaeal Tat substrates into two groups. The first group consists of substrates that are transported by TatCt alone, whereas the second group consists of substrates that are transported by the other TatC homologs (TatCo, TatCn, and TatCx). The various haloarchaea TatA components also shows the possible segregation towards the substrates. We have also identified the possible homologs for Tat substrate chaperones, which act as a quality-control mechanism for proper protein folding. Further sequence analysis implies that the two TatC domains of TatCt complement each other's functionally. Substrate analysis also revealed subtle differences between the substrates being transported by various homologs: further experimental analysis is therefore required for better understanding of the complexities of the haloarchaeal Tat pathway.
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Affiliation(s)
- Deepanjan Ghosh
- Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad- 201002, India
| | - Debjyoti Boral
- Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad- 201002, India
| | - Koteswara Rao Vankudoth
- Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad- 201002, India
| | - Sureshkumar Ramasamy
- Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Pune 411008, India
- Corresponding author.
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5
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Connelly KRS, Stevenson C, Kneuper H, Sargent F. Biosynthesis of selenate reductase in Salmonella enterica: critical roles for the signal peptide and DmsD. MICROBIOLOGY-SGM 2016; 162:2136-2146. [PMID: 27902441 PMCID: PMC5203670 DOI: 10.1099/mic.0.000381] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Salmonella enterica serovar Typhimurium is a Gram-negative bacterium with a flexible respiratory capability. Under anaerobic conditions, S. enterica can utilize a range of terminal electron acceptors, including selenate, to sustain respiratory electron transport. The S. enterica selenate reductase is a membrane-bound enzyme encoded by the ynfEFGH-dmsD operon. The active enzyme is predicted to comprise at least three subunits where YnfE is a molybdenum-containing catalytic subunit. The YnfE protein is synthesized with an N-terminal twin-arginine signal peptide and biosynthesis of the enzyme is coordinated by a signal peptide binding chaperone called DmsD. In this work, the interaction between S. enterica DmsD and the YnfE signal peptide has been studied by chemical crosslinking. These experiments were complemented by genetic approaches, which identified the DmsD binding epitope within the YnfE signal peptide. YnfE signal peptide residues L24 and A28 were shown to be important for assembly of an active selenate reductase. Conversely, a random genetic screen identified the DmsD V16 residue as being important for signal peptide recognition and selenate reductase assembly.
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Affiliation(s)
| | - Calum Stevenson
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
| | - Holger Kneuper
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
| | - Frank Sargent
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
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6
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Cherak SJ, Turner RJ. Influence of GTP on system specific chaperone - Twin arginine signal peptide interaction. Biochem Biophys Res Commun 2015; 465:753-7. [PMID: 26299930 DOI: 10.1016/j.bbrc.2015.08.079] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 08/18/2015] [Indexed: 11/30/2022]
Abstract
Many bacterial respiratory redox enzymes depend on the twin-arginine translocase (Tat) system for translocation and membrane insertion. Tat substrates contain an N-terminal twin-arginine (SRRxFLK) motif serving as the targeting signal towards the translocon. Many Tat substrates have a system specific chaperone - redox enzyme maturation protein (REMP) - for final folding and assembly prior to Tat binding. The REMP DmsD strongly interacts with the twin-arginine motif of the DmsA signal sequence of dimethyl sulfoxide (DMSO) reductase. In this study, we have utilized the in vitro protein-protein interaction technique of an affinity pull down assay, as well as protein thermal stability measurement via differential scanning fluorimetry (DSF) to investigate the interaction of guanosine nucleotides (GNPs) with DmsD. Here we have shown highly cooperative binding of DmsD with GTP. A dissociative ligand-binding style isotherm was generated upon GTP titration into the DmsD:DmsAL interaction, yielding sigmoidal release of DmsD with a Hill coefficient of 2.09 and a dissociation constant of 0.99 mM. DSF further illustrated the change in thermal stability upon DmsD interaction with DmsAL and GTP. These results imply the possibility of DmsD detection and binding of GTP during the DMSO protein maturation mechanism, from ribosomal translation to membrane targeting and final assembly. Conceivably, GTP is shown to act as a molecular regulator in the biochemical pathway.
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Affiliation(s)
- Stephana J Cherak
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada
| | - Raymond J Turner
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada.
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7
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Bay DC, Chan CS, Turner RJ. NarJ subfamily system specific chaperone diversity and evolution is directed by respiratory enzyme associations. BMC Evol Biol 2015; 15:110. [PMID: 26067063 PMCID: PMC4464133 DOI: 10.1186/s12862-015-0412-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 06/04/2015] [Indexed: 12/04/2022] Open
Abstract
Background Redox enzyme maturation proteins (REMPs) describe a diverse family of prokaryotic chaperones involved in the biogenesis of anaerobic complex iron sulfur molybdoenzyme (CISM) respiratory systems. Many REMP family studies have focused on NarJ subfamily members from Escherichia coli: NarJ, NarW, DmsD, TorD and YcdY. The aim of this bioinformatics study was to expand upon the evolution, distribution and genetic association of these 5 REMP members within 130 genome sequenced taxonomically diverse species representing 324 Prokaryotic sequences. NarJ subfamily member diversity was examined at the phylum-species level and at the amino acid/nucleotide level to determine how close their genetic associations were between their respective CISM systems within phyla. Results This study revealed that NarJ members possessed unique motifs that distinguished Gram-negative from Gram-positive/Archaeal species and identified a strict genetic association with its nitrate reductase complex (narGHI) operon compared to all other members. NarW appears to be found specifically in Gammaproteobacteria. DmsD also showed close associations with the dimethylsulfoxide reductase (dmsABC) operon compared to TorD. Phylogenetic analysis revealed that YcdY has recently evolved from DmsD and that YcdY has likely diverged into 2 subfamilies linked to Zn- dependent alkaline phosphatase (ycdX) operons and a newly identified operon containing part of Zn-metallopeptidase FtsH complex component (hflC) and NADH-quinone dehydrogenase (mdaB). TorD demonstrated the greatest diversity in operon association. TorD was identifed within operons from either trimethylamine-N-oxide reductase (torAC) or formate dehydrogenase (fdhGHI), where each type of TorD had a unique motif. Additionally a subgroup of dmsD and torD members were also linked to operons with biotin sulfoxide (bisC) and polysulfide reductase (nrfD) indicating a potential role in the maturation of diverse CISM. Conclusion Examination of diverse prokaryotic NarJ subfamily members demonstrates that the evolution and genetic association of each member is uniquely biased by its CISM operon association. Electronic supplementary material The online version of this article (doi:10.1186/s12862-015-0412-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Denice C Bay
- Department of Biological Sciences, University of Calgary, Rm 156 Biological Science Bldg., 2500 University Dr. NW, Calgary, T2N 1 N4, AB, Canada.
| | - Catherine S Chan
- Department of Biological Sciences, University of Calgary, Rm 156 Biological Science Bldg., 2500 University Dr. NW, Calgary, T2N 1 N4, AB, Canada.
| | - Raymond J Turner
- Department of Biological Sciences, University of Calgary, Rm 156 Biological Science Bldg., 2500 University Dr. NW, Calgary, T2N 1 N4, AB, Canada.
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8
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Winstone TML, Turner RJ. Thermodynamic Characterization of the DmsD Binding Site for the DmsA Twin-Arginine Motif. Biochemistry 2015; 54:2040-51. [DOI: 10.1021/bi500891d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tara M. L. Winstone
- Department of Biological
Sciences, University of Calgary, 2500 University Drive Northwest, Calgary, AB, Canada T2N 1N4
| | - Raymond J. Turner
- Department of Biological
Sciences, University of Calgary, 2500 University Drive Northwest, Calgary, AB, Canada T2N 1N4
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9
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Chan CS, Song X, Qazi SJS, Setiaputra D, Yip CK, Chao TC, Turner RJ. Unusual pairing between assistants: interaction of the twin-arginine system-specific chaperone DmsD with the chaperonin GroEL. Biochem Biophys Res Commun 2015; 456:841-6. [PMID: 25522883 DOI: 10.1016/j.bbrc.2014.12.046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 12/09/2014] [Indexed: 11/25/2022]
Abstract
DmsD is a system-specific chaperone that mediates the biogenesis and maturation of DMSO reductase in Escherichia coli. It is required for DmsAB holoenzyme formation and its targeting to the cytoplasmic membrane for translocation by the twin-arginine translocase. Previous studies suggested that DmsD also interacts with general molecular chaperones to assist in folding of the reductase subunits. Here, the interaction between DmsD and GroEL was further characterized to understand the role of GroEL in DMSO reductase maturation. The inherently weak interaction between the two was strengthened in vivo under growth conditions that induce DMSO reductase expression, and the DmsD-GroEL complex showed negligible change in hydrodynamic diameter by dynamic light scattering when cross-linked. Mapping the cross-linked sites on DmsD shows that the GroEL binding site is in close proximity to the previously characterized DmsA leader binding site. These findings support a role of GroEL in DMSO reductase maturation that likely involves its chaperonin function for assisting in folding of the DmsA preprotein.
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Affiliation(s)
- Catherine S Chan
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada; Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Xiao Song
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - S Junaid S Qazi
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Dheva Setiaputra
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Calvin K Yip
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Tzu-Chiao Chao
- Institute of Environmental Change and Society, University of Regina, Regina, Saskatchewan, Canada
| | - Raymond J Turner
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
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10
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Abstract
The transition element molybdenum (Mo) is of primordial importance for biological systems, because it is required by enzymes catalyzing key reactions in the global carbon, sulfur, and nitrogen metabolism. To gain biological activity, Mo has to be complexed by a special cofactor. With the exception of bacterial nitrogenase, all Mo-dependent enzymes contain a unique pyranopterin-based cofactor coordinating a Mo atom at their catalytic site. Various types of reactions are catalyzed by Mo-enzymes in prokaryotes including oxygen atom transfer, sulfur or proton transfer, hydroxylation, or even nonredox reactions. Mo-enzymes are widespread in prokaryotes and many of them were likely present in the Last Universal Common Ancestor. To date, more than 50--mostly bacterial--Mo-enzymes are described in nature. In a few eubacteria and in many archaea, Mo is replaced by tungsten bound to the same unique pyranopterin. How Mo-cofactor is synthesized in bacteria is reviewed as well as the way until its insertion into apo-Mo-enzymes.
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11
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‘Come into the fold’: A comparative analysis of bacterial redox enzyme maturation protein members of the NarJ subfamily. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2971-2984. [DOI: 10.1016/j.bbamem.2014.08.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 07/24/2014] [Accepted: 08/15/2014] [Indexed: 11/19/2022]
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Affiliation(s)
- Russ Hille
- Department of Biochemistry, University of California, Riverside, Riverside, California 92521, United States
| | - James Hall
- Department of Biochemistry, University of California, Riverside, Riverside, California 92521, United States
| | - Partha Basu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, United States
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13
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Rivardo F, Leach TGH, Chan CS, Winstone TML, Ladner CL, Sarfo KJ, Turner RJ. Unique Photobleaching Phenomena of the Twin-Arginine Translocase Respiratory Enzyme Chaperone DmsD. Open Biochem J 2014; 8:1-11. [PMID: 24497893 PMCID: PMC3912628 DOI: 10.2174/1874091x01408010001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2013] [Revised: 11/27/2013] [Accepted: 12/01/2013] [Indexed: 11/22/2022] Open
Abstract
DmsD is a chaperone of the redox enzyme maturation protein family specifically required for biogenesis of DMSO reductase in Escherichia coli. It exists in multiple folding forms, all of which are capable of binding its known substrate, the twin-arginine leader sequence of the DmsA catalytic subunit. It is important for maturation of the reductase and targeting to the cytoplasmic membrane for translocation. Here, we demonstrate that DmsD exhibits an irreversible photobleaching phenomenon upon 280 nm excitation irradiation. The phenomenon is due to quenching of the tryptophan residues in DmsD and is dependent on its folding and conformation. We also show that a tryptophan residue involved in DmsA signal peptide binding (W87) is important for photobleaching of DmsD. Mutation of W87, or binding of the DmsA twin-arginine signal peptide to DmsD in the pocket that includes W72, W80, and W91 significantly affects the degree of photobleaching. This study highlights the advantage of a photobleaching phenomenon to study protein folding and conformation changes within a protein that was once considered unusable in fluorescence spectroscopy.
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Affiliation(s)
- Fabrizio Rivardo
- BI 156, Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta, Canada T2N 1N4
| | - Thorin G H Leach
- BI 156, Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta, Canada T2N 1N4
| | - Catherine S Chan
- BI 156, Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta, Canada T2N 1N4
| | - Tara M L Winstone
- BI 156, Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta, Canada T2N 1N4
| | - Carol L Ladner
- BI 156, Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta, Canada T2N 1N4
| | - Kwabena J Sarfo
- BI 156, Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta, Canada T2N 1N4
| | - Raymond J Turner
- BI 156, Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta, Canada T2N 1N4
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14
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Winstone TML, Tran VA, Turner RJ. The hydrophobic region of the DmsA twin-arginine leader peptide determines specificity with chaperone DmsD. Biochemistry 2013; 52:7532-41. [PMID: 24093457 PMCID: PMC3812903 DOI: 10.1021/bi4009374] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
The
system specific chaperone DmsD plays a role in the maturation
of the catalytic subunit of dimethyl sulfoxide (DMSO) reductase, DmsA.
Pre-DmsA contains a 45-amino acid twin-arginine leader peptide that
is important for targeting and translocation of folded and cofactor-loaded
DmsA by the twin-arginine translocase. DmsD has previously been shown
to interact with the complete twin-arginine leader peptide of DmsA.
In this study, isothermal titration calorimetry was used to investigate
the thermodynamics of binding between synthetic peptides composed
of different portions of the DmsA leader peptide and DmsD. Only those
peptides that included the complete and contiguous hydrophobic region
of the DmsA leader sequence were able to bind DmsD with a 1:1 stoichiometry.
Each of the peptides that were able to bind DmsD also showed some
α-helical structure as indicated by circular dichroism spectroscopy.
Differential scanning calorimetry revealed that DmsD gained very little
thermal stability upon binding any of the DmsA leader peptides tested.
Together, these results suggest that a portion of the hydrophobic
region of the DmsA leader peptide determines the specificity of binding
and may produce helical properties
upon binding to DmsD. Overall, this study demonstrates that the recognition
of the DmsA twin-arginine leader sequence by the DmsD chaperone shows
unexpected rules and confirms further that the biochemistry of the
interaction of the chaperone with their leaders demonstrates differences
in their molecular interactions.
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Affiliation(s)
- Tara M L Winstone
- Department of Biological Sciences, University of Calgary , 2500 University Drive Northwest, Calgary, AB, Canada T2N 1N4
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15
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Stevens CM, Okon M, McIntosh LP, Paetzel M. ¹H, ¹³C and ¹⁵N resonance assignments and peptide binding site chemical shift perturbation mapping for the Escherichia coli redox enzyme chaperone DmsD. BIOMOLECULAR NMR ASSIGNMENTS 2013; 7:193-197. [PMID: 22766963 DOI: 10.1007/s12104-012-9408-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Accepted: 06/21/2012] [Indexed: 06/01/2023]
Abstract
Herein are reported the mainchain (1)H, (13)C and (15)N chemical shift assignments and amide (15)N relaxation data for Escherichia coli DmsD, a 23.3 kDa protein responsible for the correct folding and translocation of the dimethyl sulfoxide reductase enzyme complex. In addition, the observed amide chemical shift perturbations resulting from complex formation with the reductase subunit DmsA leader peptide support a model in which the 44 residue peptide makes extensive contacts across the surface of the DmsD protein.
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Affiliation(s)
- Charles M Stevens
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
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16
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Abstract
The Tat (twin-arginine translocation) system is a protein targeting pathway utilized by prokaryotes and chloroplasts. Tat substrates are produced with distinctive N-terminal signal peptides and are translocated as fully folded proteins. In Escherichia coli, Tat-dependent proteins often contain redox cofactors that must be loaded before translocation. Trimethylamine N-oxide reductase (TorA) is a model bacterial Tat substrate and is a molybdenum cofactor-dependent enzyme. Co-ordination of cofactor loading and translocation of TorA is directed by the TorD protein, which is a cytoplasmic chaperone known to interact physically with the TorA signal peptide. In the present study, a pre-export TorAD complex has been characterized using biochemical and biophysical techniques, including SAXS (small-angle X-ray scattering). A stable, cofactor-free TorAD complex was isolated, which revealed a 1:1 binding stoichiometry. Surprisingly, a TorAD complex with similar architecture can be isolated in the complete absence of the 39-residue TorA signal peptide. The present study demonstrates that two high-affinity binding sites for TorD are present on TorA, and that a single TorD protein binds both of those simultaneously. Further characterization suggested that the C-terminal ‘Domain IV’ of TorA remained solvent-exposed in the cofactor-free pre-export TorAD complex. It is possible that correct folding of Domain IV upon cofactor loading is the trigger for TorD release and subsequent export of TorA.
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Iobbi-Nivol C, Leimkühler S. Molybdenum enzymes, their maturation and molybdenum cofactor biosynthesis in Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012. [PMID: 23201473 DOI: 10.1016/j.bbabio.2012.11.007] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Molybdenum cofactor (Moco) biosynthesis is an ancient, ubiquitous, and highly conserved pathway leading to the biochemical activation of molybdenum. Moco is the essential component of a group of redox enzymes, which are diverse in terms of their phylogenetic distribution and their architectures, both at the overall level and in their catalytic geometry. A wide variety of transformations are catalyzed by these enzymes at carbon, sulfur and nitrogen atoms, which include the transfer of an oxo group or two electrons to or from the substrate. More than 50 molybdoenzymes were identified in bacteria to date. In molybdoenzymes Mo is coordinated to a dithiolene group on the 6-alkyl side chain of a pterin called molybdopterin (MPT). The biosynthesis of Moco can be divided into four general steps in bacteria: 1) formation of the cyclic pyranopterin monophosphate, 2) formation of MPT, 3) insertion of molybdenum into molybdopterin to form Moco, and 4) additional modification of Moco with the attachment of GMP or CMP to the phosphate group of MPT, forming the dinucleotide variant of Moco. This review will focus on molybdoenzymes, the biosynthesis of Moco, and its incorporation into specific target proteins focusing on Escherichia coli. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.
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Affiliation(s)
- Chantal Iobbi-Nivol
- Institut de Microbiologie de la Méditerranée, Aix Marseille Université, Marseille, France
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18
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Lorenzi M, Sylvi L, Gerbaud G, Mileo E, Halgand F, Walburger A, Vezin H, Belle V, Guigliarelli B, Magalon A. Conformational selection underlies recognition of a molybdoenzyme by its dedicated chaperone. PLoS One 2012. [PMID: 23185350 PMCID: PMC3501500 DOI: 10.1371/journal.pone.0049523] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Molecular recognition is central to all biological processes. Understanding the key role played by dedicated chaperones in metalloprotein folding and assembly requires the knowledge of their conformational ensembles. In this study, the NarJ chaperone dedicated to the assembly of the membrane-bound respiratory nitrate reductase complex NarGHI, a molybdenum-iron containing metalloprotein, was taken as a model of dedicated chaperone. The combination of two techniques ie site-directed spin labeling followed by EPR spectroscopy and ion mobility mass spectrometry, was used to get information about the structure and conformational dynamics of the NarJ chaperone upon binding the N-terminus of the NarG metalloprotein partner. By the study of singly spin-labeled proteins, the E119 residue present in a conserved elongated hydrophobic groove of NarJ was shown to be part of the interaction site. Moreover, doubly spin-labeled proteins studied by pulsed double electron-electron resonance (DEER) spectroscopy revealed a large and composite distribution of inter-label distances that evolves into a single preexisting one upon complex formation. Additionally, ion mobility mass spectrometry experiments fully support these findings by revealing the existence of several conformers in equilibrium through the distinction of different drift time curves and the selection of one of them upon complex formation. Taken together our work provides a detailed view of the structural flexibility of a dedicated chaperone and suggests that the exquisite recognition and binding of the N-terminus of the metalloprotein is governed by a conformational selection mechanism.
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Affiliation(s)
- Magali Lorenzi
- Unité de Bioénergétique et Ingénierie des Protéines (UMR7281), Institut de Microbiologie de la Méditerranée, CNRS & Aix-Marseille Univ, Marseille, France
| | - Léa Sylvi
- Laboratoire de Chimie Bactérienne (UMR7283), Institut de Microbiologie de la Méditerranée, CNRS & Aix-Marseille Univ, Marseille, France
| | - Guillaume Gerbaud
- Unité de Bioénergétique et Ingénierie des Protéines (UMR7281), Institut de Microbiologie de la Méditerranée, CNRS & Aix-Marseille Univ, Marseille, France
| | - Elisabetta Mileo
- Unité de Bioénergétique et Ingénierie des Protéines (UMR7281), Institut de Microbiologie de la Méditerranée, CNRS & Aix-Marseille Univ, Marseille, France
| | - Frédéric Halgand
- Unité de Bioénergétique et Ingénierie des Protéines (UMR7281), Institut de Microbiologie de la Méditerranée, CNRS & Aix-Marseille Univ, Marseille, France
| | - Anne Walburger
- Laboratoire de Chimie Bactérienne (UMR7283), Institut de Microbiologie de la Méditerranée, CNRS & Aix-Marseille Univ, Marseille, France
| | - Hervé Vezin
- Laboratoire de Spectrochimie Infrarouge et Raman (UMR8516), Villeneuve d'Ascq, France
| | - Valérie Belle
- Unité de Bioénergétique et Ingénierie des Protéines (UMR7281), Institut de Microbiologie de la Méditerranée, CNRS & Aix-Marseille Univ, Marseille, France
- * E-mail: (VB); (AM)
| | - Bruno Guigliarelli
- Unité de Bioénergétique et Ingénierie des Protéines (UMR7281), Institut de Microbiologie de la Méditerranée, CNRS & Aix-Marseille Univ, Marseille, France
| | - Axel Magalon
- Laboratoire de Chimie Bactérienne (UMR7283), Institut de Microbiologie de la Méditerranée, CNRS & Aix-Marseille Univ, Marseille, France
- * E-mail: (VB); (AM)
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19
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Purification of a Tat leader peptide by co-expression with its chaperone. Protein Expr Purif 2012; 84:167-72. [DOI: 10.1016/j.pep.2012.05.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 05/03/2012] [Accepted: 05/06/2012] [Indexed: 11/22/2022]
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20
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Shanmugham A, Bakayan A, Völler P, Grosveld J, Lill H, Bollen YJM. The hydrophobic core of twin-arginine signal sequences orchestrates specific binding to Tat-pathway related chaperones. PLoS One 2012; 7:e34159. [PMID: 22479549 PMCID: PMC3316669 DOI: 10.1371/journal.pone.0034159] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 02/27/2012] [Indexed: 11/19/2022] Open
Abstract
Redox enzyme maturation proteins (REMPs) bind pre-proteins destined for translocation across the bacterial cytoplasmic membrane via the twin-arginine translocation system and enable the enzymatic incorporation of complex cofactors. Most REMPs recognize one specific pre-protein. The recognition site usually resides in the N-terminal signal sequence. REMP binding protects signal peptides against degradation by proteases. REMPs are also believed to prevent binding of immature pre-proteins to the translocon. The main aim of this work was to better understand the interaction between REMPs and substrate signal sequences. Two REMPs were investigated: DmsD (specific for dimethylsulfoxide reductase, DmsA) and TorD (specific for trimethylamine N-oxide reductase, TorA). Green fluorescent protein (GFP) was genetically fused behind the signal sequences of TorA and DmsA. This ensures native behavior of the respective signal sequence and excludes any effects mediated by the mature domain of the pre-protein. Surface plasmon resonance analysis revealed that these chimeric pre-proteins specifically bind to the cognate REMP. Furthermore, the region of the signal sequence that is responsible for specific binding to the corresponding REMP was identified by creating region-swapped chimeric signal sequences, containing parts of both the TorA and DmsA signal sequences. Surprisingly, specificity is not encoded in the highly variable positively charged N-terminal region of the signal sequence, but in the more similar hydrophobic C-terminal parts. Interestingly, binding of DmsD to its model substrate reduced membrane binding of the pre-protein. This property could link REMP-signal peptide binding to its reported proofreading function.
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Affiliation(s)
| | | | | | | | | | - Yves J. M. Bollen
- Department of Molecular Cell Biology, VU University Amsterdam, Amsterdam, The Netherlands
- * E-mail:
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21
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Grahl S, Maillard J, Spronk CAEM, Vuister GW, Sargent F. Overlapping transport and chaperone-binding functions within a bacterial twin-arginine signal peptide. Mol Microbiol 2012; 83:1254-67. [PMID: 22329966 PMCID: PMC3712460 DOI: 10.1111/j.1365-2958.2012.08005.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The twin-arginine translocation (Tat) pathway is a protein targeting system present in many prokaryotes. The physiological role of the Tat pathway is the transmembrane translocation of fully-folded proteins, which are targeted by N-terminal signal peptides bearing conserved SRRxFLK ‘twin-arginine’ amino acid motifs. In Escherichia coli the majority of Tat targeted proteins bind redox cofactors and it is important that only mature, cofactor-loaded precursors are presented for export. Cellular processes have been unearthed that sequence these events, for example the signal peptide of the periplasmic nitrate reductase (NapA) is bound by a cytoplasmic chaperone (NapD) that is thought to regulate assembly and export of the enzyme. In this work, genetic, biophysical and structural approaches were taken to dissect the interaction between NapD and the NapA signal peptide. A NapD binding epitope was identified towards the N-terminus of the signal peptide, which overlapped significantly with the twin-arginine targeting motif. NMR spectroscopy revealed that the signal peptide adopted a α-helical conformation when bound by NapD, and substitution of single residues within the NapA signal peptide was sufficient to disrupt the interaction. This work provides an increased level of understanding of signal peptide function on the bacterial Tat pathway.
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Affiliation(s)
- Sabine Grahl
- College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
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Coulthurst SJ, Dawson A, Hunter WN, Sargent F. Conserved signal peptide recognition systems across the prokaryotic domains. Biochemistry 2012; 51:1678-86. [PMID: 22289056 PMCID: PMC3290102 DOI: 10.1021/bi201852d] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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The twin-arginine translocation (Tat) pathway is a protein
targeting system found in bacteria, archaea, and chloroplasts. Proteins
are directed to the Tat translocase by N-terminal signal peptides
containing SRRxFLK “twin-arginine” amino acid motifs.
The key feature of the Tat system is its ability to transport fully
folded proteins across ionically sealed membranes. For this reason
the Tat pathway has evolved for the assembly of extracytoplasmic redox
enzymes that must bind cofactors, and so fold, prior to export. It
is important that only cofactor-loaded, folded precursors are presented
for export, and cellular processes have been unearthed that regulate
signal peptide activity. One mechanism, termed “Tat proofreading”,
involves specific signal peptide binding proteins or chaperones. The
archetypal Tat proofreading chaperones belong to the TorD family,
which are dedicatedto the assembly of molybdenum-dependent redox
enzymes in bacteria. Here, a gene cluster was identified in the archaeon Archaeoglobus fulgidusthat is predicted to encode a putative
molybdenum-dependent tetrathionate reductase. The gene cluster also
encodes a TorD family chaperone (AF0160 or TtrD) and in this work
TtrD is shown to bind specifically to the Tat signal peptide of the
TtrA subunit of the tetrathionate reductase. In addition, the 3D crystal
structure of TtrD is presented at 1.35 Å resolution and a nine-residue
binding epitope for TtrD is identified within the TtrA signal peptide
close to the twin-arginine targeting motif. This work suggests that
archaea may employ a chaperone-dependent Tat proofreading system that
is similar to that utilized by bacteria.
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Affiliation(s)
- Sarah J Coulthurst
- College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
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23
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Hou B, Brüser T. The Tat-dependent protein translocation pathway. Biomol Concepts 2011; 2:507-23. [DOI: 10.1515/bmc.2011.040] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 08/05/2011] [Indexed: 11/15/2022] Open
Abstract
AbstractThe twin-arginine translocation (Tat) pathway is found in bacteria, archaea, and plant chloroplasts, where it is dedicated to the transmembrane transport of fully folded proteins. These proteins contain N-terminal signal peptides with a specific Tat-system binding motif that is recognized by the transport machinery. In contrast to other protein transport systems, the Tat system consists of multiple copies of only two or three usually small (∼8–30 kDa) membrane proteins that oligomerize to two large complexes that transiently interact during translocation. Only one of these complexes includes a polytopic membrane protein, TatC. The other complex consists of TatA. Tat systems of plants, proteobacteria, and several other phyla contain a third component, TatB. TatB is evolutionarily and structurally related to TatA and usually forms tight complexes with TatC. Minimal two-component Tat systems lacking TatB are found in many bacterial and archaeal phyla. They consist of a ‘bifunctional’ TatA that also covers TatB functionalities, and a TatC. Recent insights into the structure and interactions of the Tat proteins have various important implications.
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Affiliation(s)
- Bo Hou
- Institute of Microbiology, Leibniz University Hannover, Schneiderberg 50, D-30167 Hannover, Germany
| | - Thomas Brüser
- Institute of Microbiology, Leibniz University Hannover, Schneiderberg 50, D-30167 Hannover, Germany
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24
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Magalon A, Fedor JG, Walburger A, Weiner JH. Molybdenum enzymes in bacteria and their maturation. Coord Chem Rev 2011. [DOI: 10.1016/j.ccr.2010.12.031] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Tang H, Rothery RA, Voss JE, Weiner JH. Correct assembly of iron-sulfur cluster FS0 into Escherichia coli dimethyl sulfoxide reductase (DmsABC) is a prerequisite for molybdenum cofactor insertion. J Biol Chem 2011; 286:15147-54. [PMID: 21357619 DOI: 10.1074/jbc.m110.213306] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The FS0 [4Fe-4S] cluster of the catalytic subunit (DmsA) of Escherichia coli dimethyl sulfoxide reductase (DmsABC) plays a key role in the electron transfer relay. We have now established an additional role for the cluster in directing molybdenum cofactor assembly during enzyme maturation. EPR spectroscopy indicates that FS0 has a high spin ground state (S = 3/2) in its reduced form, resulting in an EPR spectrum with a peak at g ∼ 5.0. The cluster is predicted to be in close proximity to the molybdo-bis(pyranopterin guanine dinucleotide) (Mo-bisPGD) cofactor, which provides the site of dimethyl sulfoxide reduction. Comparison with nitrate reductase A (NarGHI) indicates that a sequence of residues ((18)CTVNC(22)) plays a role in both FS0 and Mo-bisPGD coordination. A DmsA(ΔN21) mutant prevented Mo-bisPGD binding and resulted in a degenerate [3Fe-4S] cluster form of FS0 being assembled. DmsA belongs to the Type II subclass of Mo-bisPGD-containing catalytic subunits that is distinguished from the Type I subclass by having three rather than two residues between the first two Cys residues coordinating FS0 and a conserved Arg residue rather than a Lys residue following the fourth cluster coordinating Cys. We introduced a Type I Cys group into DmsA in two stages. We changed its sequence from (18)C(A)TVNC(B)GSRC(C)P(27) to (18)C(A)TYC(B)GVGC(C)G(26) (similar to that of formate dehydrogenase (FdnG)) and demonstrated that this eliminated both Mo-bisPGD binding and EPR-detectable FS0. We then combined this change with a DmsA(R61K) mutation and demonstrated that this additional change partially rescued Mo-bisPGD insertion.
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Affiliation(s)
- Huipo Tang
- Department of Biochemistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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Chan CS, Chang L, Winstone TML, Turner RJ. Comparing system-specific chaperone interactions with their Tat dependent redox enzyme substrates. FEBS Lett 2010; 584:4553-8. [PMID: 20974141 DOI: 10.1016/j.febslet.2010.10.043] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Revised: 09/16/2010] [Accepted: 10/17/2010] [Indexed: 12/01/2022]
Abstract
Redox enzyme substrates of the twin-arginine translocation (Tat) system contain a RR-motif in their leader peptide and require the assistance of chaperones, redox enzyme maturation proteins (REMPs). Here various regions of the RR-containing oxidoreductase subunit (leader peptide, full preprotein with and without a leader cleavage site, mature protein) were assayed for interaction with their REMPs. All REMPs bound their preprotein substrates independent of the cleavage site. Some showed binding to either the leader or mature region, whereas in one case only the preprotein bound its REMP. The absence of Tat also influenced the amount of chaperone-substrate interaction.
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Affiliation(s)
- Catherine S Chan
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, Alberta, Canada
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Abstract
Proteins that reside partially or completely outside the bacterial cytoplasm require specialized pathways to facilitate their localization. Globular proteins that function in the periplasm must be translocated across the hydrophobic barrier of the inner membrane. While the Sec pathway transports proteins in a predominantly unfolded conformation, the Tat pathway exports folded protein substrates. Protein transport by the Tat machinery is powered solely by the transmembrane proton gradient, and there is no requirement for nucleotide triphosphate hydrolysis. Proteins are targeted to the Tat machinery by N-terminal signal peptides that contain a consensus twin arginine motif. In Escherichia coli and Salmonella there are approximately thirty proteins with twin arginine signal peptides that are transported by the Tat pathway. The majority of these bind complex redox cofactors such as iron sulfur clusters or the molybdopterin cofactor. Here we describe what is known about Tat substrates in E. coli and Salmonella, the function and mechanism of Tat protein export, and how the cofactor insertion step is coordinated to ensure that only correctly assembled substrates are targeted to the Tat machinery.
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28
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Guymer D, Maillard J, Agacan MF, Brearley CA, Sargent F. Intrinsic GTPase activity of a bacterial twin-arginine translocation proofreading chaperone induced by domain swapping. FEBS J 2010; 277:511-25. [PMID: 20064164 DOI: 10.1111/j.1742-4658.2009.07507.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The bacterial twin-arginine translocation (Tat) system is a protein targeting pathway dedicated to the transport of folded proteins across the cytoplasmic membrane. Proteins transported on the Tat pathway are synthesised as precursors with N-terminal signal peptides containing a conserved amino acid motif. In Escherichia coli, many Tat substrates contain prosthetic groups and undergo cytoplasmic assembly processes prior to the translocation event. A pre-export 'Tat proofreading' process, mediated by signal peptide-binding chaperones, is considered to prevent premature export of some Tat-targeted proteins until all other assembly processes are complete. TorD is a paradigm Tat proofreading chaperone and co-ordinates the maturation and export of the periplasmic respiratory enzyme trimethylamine N-oxide reductase (TorA). Although it is well established that TorD binds directly to the TorA signal peptide, the mechanism of regulation or control of binding is not understood. Previous structural analyses of TorD homologues showed that these proteins can exist as monomeric and domain-swapped dimeric forms. In the present study, we demonstrate that isolated recombinant TorD exhibits a magnesium-dependent GTP hydrolytic activity, despite the absence of classical nucleotide-binding motifs in the protein. TorD GTPase activity is shown to be present only in the domain-swapped homodimeric form of the protein, thus defining a biochemical role for the oligomerisation. Site-directed mutagenesis identified one TorD side-chain (D68) that was important in substrate selectivity. A D68W variant TorD protein was found to exhibit an ATPase activity not observed for native TorD, and an in vivo assay established that this variant was defective in the Tat proofreading process.
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Affiliation(s)
- David Guymer
- College of Life Sciences, University of Dundee, Dundee, UK
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Ramasamy SK, Clemons WM. Structure of the twin-arginine signal-binding protein DmsD from Escherichia coli. Acta Crystallogr Sect F Struct Biol Cryst Commun 2009; 65:746-50. [PMID: 19652330 DOI: 10.1107/s1744309109023811] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Accepted: 06/21/2009] [Indexed: 11/10/2022]
Abstract
The translocation of folded proteins via the twin-arginine translocation (Tat) pathway is regulated to prevent the futile export of inactive substrate. DmsD is part of a class of cytoplasmic chaperones that play a role in preventing certain redox proteins from premature transport. DmsD from Escherichia coli has been crystallized in space group P4(1)2(1)2, with unit-cell parameters a = b = 97.45, c = 210.04 A, in the presence of a small peptide. The structure has been solved by molecular replacement to a resolution of 2.4 A and refined to an R factor of 19.4%. There are four molecules in the asymmetric unit that may mimic a higher order structure in vivo. There appears to be density for the peptide in a predicted binding pocket, which lends support to its role as the signal-recognition surface for this class of proteins.
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Affiliation(s)
- Suresh Kumar Ramasamy
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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