1
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Nair AG, Perumalla DS, Anjukandi P. Towards solvent regulated self-activation of N-terminal disulfide bond oxidoreductase-D. Phys Chem Chem Phys 2022; 24:7691-7699. [PMID: 35311864 DOI: 10.1039/d1cp05819c] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
N-terminal disulfide bond oxidoreductase-D (nDsbD), an essential redox enzyme in Gram-negative bacteria, consists of a single disulfide bond (Cys103-Cys109) in its active site. The enzymatic functions are believed to be regulated by an electron transfer mediated redox switching of the disulfide bond, which is vital in controlling bacterial virulence factors. In light of the disulfide bond's inclination towards nucleophilic cleavage, it is also plausible that an internal nucleophile could second the existing electron transfer mechanism in nDsbD. Using QM/MM MD metadynamics simulations, we explore different possibilities of generating an internal nucleophile near the nDsbD active site, which could serve as a fail-over mechanism in cleaving the disulfide bond. The simulations show the formation of the internal nucleophile Tyr42O- (F ≈ 9 kcal mol-1) and its stabilization through the solvent medium. The static gas-phase calculations show that Tyr42O- could be a potential nucleophile for cleaving the S-S bond. Most strikingly, it is also seen that Tyr42O- and Asp68OH communicate with each other through a proton-hole like water wire (F ≈ 12 kcal mol-1), thus modulating the nucleophile formation. Accordingly, we propose the role of a solvent in regulating the internal nucleophilic reactions and the subsequent self-activation of nDsbD. We believe that this could be deterministic while designing enzyme-targeted inhibitor compounds.
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Affiliation(s)
- Aparna G Nair
- Department of Chemistry, Indian Institute of Technology, Palakkad-678557, Kerala, India.
| | | | - Padmesh Anjukandi
- Department of Chemistry, Indian Institute of Technology, Palakkad-678557, Kerala, India.
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2
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Shui S, Gainza P, Scheller L, Yang C, Kurumida Y, Rosset S, Georgeon S, Di Roberto RB, Castellanos-Rueda R, Reddy ST, Correia BE. A rational blueprint for the design of chemically-controlled protein switches. Nat Commun 2021; 12:5754. [PMID: 34599176 PMCID: PMC8486872 DOI: 10.1038/s41467-021-25735-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Accepted: 08/24/2021] [Indexed: 12/20/2022] Open
Abstract
Small-molecule responsive protein switches are crucial components to control synthetic cellular activities. However, the repertoire of small-molecule protein switches is insufficient for many applications, including those in the translational spaces, where properties such as safety, immunogenicity, drug half-life, and drug side-effects are critical. Here, we present a computational protein design strategy to repurpose drug-inhibited protein-protein interactions as OFF- and ON-switches. The designed binders and drug-receptors form chemically-disruptable heterodimers (CDH) which dissociate in the presence of small molecules. To design ON-switches, we converted the CDHs into a multi-domain architecture which we refer to as activation by inhibitor release switches (AIR) that incorporate a rationally designed drug-insensitive receptor protein. CDHs and AIRs showed excellent performance as drug responsive switches to control combinations of synthetic circuits in mammalian cells. This approach effectively expands the chemical space and logic responses in living cells and provides a blueprint to develop new ON- and OFF-switches. Small-molecule responsive protein switches are crucial components to control synthetic cellular activities. Here, we present a computational protein design strategy to repurpose drug-inhibited protein-protein interactions into OFF- and ON-switches active in cells.
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Affiliation(s)
- Sailan Shui
- Laboratory of Protein Design and Immunoengineering (LPDI) - STI - EPFL, Lausanne, Switzerland.,Swiss Institute of Bioinformatics (SIB), Lausanne, CH-1015, Switzerland
| | - Pablo Gainza
- Laboratory of Protein Design and Immunoengineering (LPDI) - STI - EPFL, Lausanne, Switzerland.,Swiss Institute of Bioinformatics (SIB), Lausanne, CH-1015, Switzerland
| | - Leo Scheller
- Laboratory of Protein Design and Immunoengineering (LPDI) - STI - EPFL, Lausanne, Switzerland.,Swiss Institute of Bioinformatics (SIB), Lausanne, CH-1015, Switzerland
| | - Che Yang
- Laboratory of Protein Design and Immunoengineering (LPDI) - STI - EPFL, Lausanne, Switzerland.,Swiss Institute of Bioinformatics (SIB), Lausanne, CH-1015, Switzerland
| | - Yoichi Kurumida
- Department of Life Science, School and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8550, Japan
| | - Stéphane Rosset
- Laboratory of Protein Design and Immunoengineering (LPDI) - STI - EPFL, Lausanne, Switzerland.,Swiss Institute of Bioinformatics (SIB), Lausanne, CH-1015, Switzerland
| | - Sandrine Georgeon
- Laboratory of Protein Design and Immunoengineering (LPDI) - STI - EPFL, Lausanne, Switzerland.,Swiss Institute of Bioinformatics (SIB), Lausanne, CH-1015, Switzerland
| | - Raphaël B Di Roberto
- Department of Biosystems Science and Engineering, ETH Zürich, 4058, Basel, Switzerland
| | | | - Sai T Reddy
- Department of Biosystems Science and Engineering, ETH Zürich, 4058, Basel, Switzerland
| | - Bruno E Correia
- Laboratory of Protein Design and Immunoengineering (LPDI) - STI - EPFL, Lausanne, Switzerland. .,Swiss Institute of Bioinformatics (SIB), Lausanne, CH-1015, Switzerland.
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3
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Smith RP, Mohanty B, Mowlaboccus S, Paxman JJ, Williams ML, Headey SJ, Wang G, Subedi P, Doak BC, Kahler CM, Scanlon MJ, Heras B. Structural and biochemical insights into the disulfide reductase mechanism of DsbD, an essential enzyme for neisserial pathogens. J Biol Chem 2018; 293:16559-16571. [PMID: 30181210 DOI: 10.1074/jbc.ra118.004847] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 08/16/2018] [Indexed: 12/13/2022] Open
Abstract
The worldwide incidence of neisserial infections, particularly gonococcal infections, is increasingly associated with antibiotic-resistant strains. In particular, extensively drug-resistant Neisseria gonorrhoeae strains that are resistant to third-generation cephalosporins are a major public health concern. There is a pressing clinical need to identify new targets for the development of antibiotics effective against Neisseria-specific processes. In this study, we report that the bacterial disulfide reductase DsbD is highly prevalent and conserved among Neisseria spp. and that this enzyme is essential for survival of N. gonorrhoeae DsbD is a membrane-bound protein that consists of two periplasmic domains, n-DsbD and c-DsbD, which flank the transmembrane domain t-DsbD. In this work, we show that the two functionally essential periplasmic domains of Neisseria DsbD catalyze electron transfer reactions through unidirectional interdomain interactions, from reduced c-DsbD to oxidized n-DsbD, and that this process is not dictated by their redox potentials. Structural characterization of the Neisseria n- and c-DsbD domains in both redox states provides evidence that steric hindrance reduces interactions between the two periplasmic domains when n-DsbD is reduced, thereby preventing a futile redox cycle. Finally, we propose a conserved mechanism of electron transfer for DsbD and define the residues involved in domain-domain recognition. Inhibitors of the interaction of the two DsbD domains have the potential to be developed as anti-neisserial agents.
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Affiliation(s)
- Roxanne P Smith
- From the Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3086, Victoria, Australia
| | - Biswaranjan Mohanty
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne 3052, Victoria, Australia, and
| | - Shakeel Mowlaboccus
- the Marshall Center for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Perth 6907, Western Australia, Australia
| | - Jason J Paxman
- From the Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3086, Victoria, Australia
| | - Martin L Williams
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne 3052, Victoria, Australia, and
| | - Stephen J Headey
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne 3052, Victoria, Australia, and
| | - Geqing Wang
- From the Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3086, Victoria, Australia
| | - Pramod Subedi
- From the Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3086, Victoria, Australia
| | - Bradley C Doak
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne 3052, Victoria, Australia, and
| | - Charlene M Kahler
- the Marshall Center for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Perth 6907, Western Australia, Australia
| | - Martin J Scanlon
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne 3052, Victoria, Australia, and
| | - Begoña Heras
- From the Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3086, Victoria, Australia,
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4
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Smith RP, Mohanty B, Williams ML, Scanlon MJ, Heras B. H N, N, C α and C β assignments of the two periplasmic domains of Neisseria meningitidis DsbD. BIOMOLECULAR NMR ASSIGNMENTS 2017; 11:181-186. [PMID: 28589218 DOI: 10.1007/s12104-017-9743-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 05/26/2017] [Indexed: 06/07/2023]
Abstract
DsbD is a disulfide bond reductase present in the inner membrane of many Gamma-Proteobacteria. In the human pathogen Neisseria meningitidis, DsbD is required for viability and represents a potential target for the development of antibiotics. Here we report the chemical shift assignments (HN, N, Cα and Cβ) for the reduced and oxidized forms of the two periplasmic domains of N. meningitidis DsbD, n-NmDsbD and c-NmDsbD. The backbone amide resonances in all four forms were completely assigned, and the secondary structures for the core regions of the proteins were calculated using 13Cαβ shifts. The reduced and oxidized forms of each domain have similar secondary shifts suggesting they retain the same fold. We anticipate that these data will provide an important basis for studying the interaction between n-NmDsbD and c-NmDsbD, which is required for electron transfer across the bacterial cytoplasmic membrane.
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Affiliation(s)
- Roxanne P Smith
- La Trobe Institute for Molecular Science, La Trobe University, Bundoora, VIC, Australia
| | - Biswaranjan Mohanty
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Martin L Williams
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Martin J Scanlon
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia.
| | - Begoña Heras
- La Trobe Institute for Molecular Science, La Trobe University, Bundoora, VIC, Australia
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5
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Bacterial thiol oxidoreductases - from basic research to new antibacterial strategies. Appl Microbiol Biotechnol 2017; 101:3977-3989. [PMID: 28409380 PMCID: PMC5403849 DOI: 10.1007/s00253-017-8291-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 04/03/2017] [Accepted: 04/04/2017] [Indexed: 12/15/2022]
Abstract
The recent, rapid increase in bacterial antimicrobial resistance has become a major public health concern. One approach to generate new classes of antibacterials is targeting virulence rather than the viability of bacteria. Proteins of the Dsb system, which play a key role in the virulence of many pathogenic microorganisms, represent potential new drug targets. The first part of the article presents current knowledge of how the Dsb system impacts function of various protein secretion systems that influence the virulence of many pathogenic bacteria. Next, the review describes methods used to study the structure, biochemistry, and microbiology of the Dsb proteins and shows how these experiments broaden our knowledge about their function. The lessons gained from basic research have led to a specific search for inhibitors blocking the Dsb networks.
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6
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Bocian-Ostrzycka KM, Łasica AM, Dunin-Horkawicz S, Grzeszczuk MJ, Drabik K, Dobosz AM, Godlewska R, Nowak E, Collet JF, Jagusztyn-Krynicka EK. Functional and evolutionary analyses of Helicobacter pylori HP0231 (DsbK) protein with strong oxidative and chaperone activity characterized by a highly diverged dimerization domain. Front Microbiol 2015; 6:1065. [PMID: 26500620 PMCID: PMC4597128 DOI: 10.3389/fmicb.2015.01065] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 09/16/2015] [Indexed: 12/15/2022] Open
Abstract
Helicobacter pylori does not encode the classical DsbA/DsbB oxidoreductases that are crucial for oxidative folding of extracytoplasmic proteins. Instead, this microorganism encodes an untypical two proteins playing a role in disulfide bond formation – periplasmic HP0231, which structure resembles that of EcDsbC/DsbG, and its redox partner, a membrane protein HpDsbI (HP0595) with a β-propeller structure. The aim of presented work was to assess relations between HP0231 structure and function. We showed that HP0231 is most closely related evolutionarily to the catalytic domain of DsbG, even though it possesses a catalytic motif typical for canonical DsbA proteins. Similarly, the highly diverged N-terminal dimerization domain is homologous to the dimerization domain of DsbG. To better understand the functioning of this atypical oxidoreductase, we examined its activity using in vivo and in vitro experiments. We found that HP0231 exhibits oxidizing and chaperone activities but no isomerizing activity, even though H. pylori does not contain a classical DsbC. We also show that HP0231 is not involved in the introduction of disulfide bonds into HcpC (Helicobactercysteine-rich protein C), a protein involved in the modulation of the H. pylori interaction with its host. Additionally, we also constructed a truncated version of HP0231 lacking the dimerization domain, denoted HP0231m, and showed that it acts in Escherichia coli cells in a DsbB-dependent manner. In contrast, HP0231m and classical monomeric EcDsbA (E. coli DsbA protein) were both unable to complement the lack of HP0231 in H. pylori cells, though they exist in oxidized forms. HP0231m is inactive in the insulin reduction assay and possesses high chaperone activity, in contrast to EcDsbA. In conclusion, HP0231 combines oxidative functions characteristic of DsbA proteins and chaperone activity characteristic of DsbC/DsbG, and it lacks isomerization activity.
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Affiliation(s)
- Katarzyna M Bocian-Ostrzycka
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
| | - Anna M Łasica
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology Warsaw, Poland
| | - Stanisław Dunin-Horkawicz
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology Warsaw, Poland
| | - Magdalena J Grzeszczuk
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
| | - Karolina Drabik
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
| | - Aneta M Dobosz
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
| | - Renata Godlewska
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
| | - Elżbieta Nowak
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology Warsaw, Poland
| | - Jean-Francois Collet
- de Duve Institute, Université catholique de Louvain (UCL)/Walloon Excellence in Life Sciences and Biotechnology Brussels, Belgium
| | - Elżbieta K Jagusztyn-Krynicka
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
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7
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Mavridou DAI, Saridakis E, Kritsiligkou P, Mozley EC, Ferguson SJ, Redfield C. An extended active-site motif controls the reactivity of the thioredoxin fold. J Biol Chem 2014; 289:8681-96. [PMID: 24469455 PMCID: PMC3961690 DOI: 10.1074/jbc.m113.513457] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Proteins belonging to the thioredoxin (Trx) superfamily are abundant in all organisms. They share the same structural features, arranged in a seemingly simple fold, but they perform a multitude of functions in oxidative protein folding and electron transfer pathways. We use the C-terminal domain of the unique transmembrane reductant conductor DsbD as a model for an in-depth analysis of the factors controlling the reactivity of the Trx fold. We employ NMR spectroscopy, x-ray crystallography, mutagenesis, in vivo functional experiments applied to DsbD, and a comparative sequence analysis of Trx-fold proteins to determine the effect of residues in the vicinity of the active site on the ionization of the key nucleophilic cysteine of the -CXXC- motif. We show that the function and reactivity of Trx-fold proteins depend critically on the electrostatic features imposed by an extended active-site motif.
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Affiliation(s)
- Despoina A I Mavridou
- From the Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom and
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8
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Yoon JY, Kim J, An DR, Lee SJ, Kim HS, Im HN, Yoon HJ, Kim JY, Kim SJ, Han BW, Suh SW. Structural and functional characterization of HP0377, a thioredoxin-fold protein from Helicobacter pylori. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:735-46. [PMID: 23633582 DOI: 10.1107/s0907444913001236] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 01/12/2013] [Indexed: 12/16/2022]
Abstract
Maturation of cytochrome c is carried out in the bacterial periplasm, where specialized thiol-disulfide oxidoreductases provide the correct reduction of oxidized apocytochrome c before covalent haem attachment. HP0377 from Helicobacter pylori is a thioredoxin-fold protein that has been implicated as a component of system II for cytochrome c assembly and shows limited sequence similarity to Escherichia coli DsbC, a disulfide-bond isomerase. To better understand the role of HP0377, its crystal structures have been determined in both reduced and partially oxidized states, which are highly similar to each other. Sedimentation-equilibrium experiments indicate that HP0377 is monomeric in solution. HP0377 adopts a thioredoxin fold but shows distinctive variations as in other thioredoxin-like bacterial periplasmic proteins. The active site of HP0377 closely resembles that of E. coli DsbC. A reductase assay suggests that HP0377 may play a role as a reductase in the biogenesis of holocytochrome c553 (HP1227). Binding experiments indicate that it can form a covalent complex with HP0518, a putative L,D-transpeptidase with a catalytic cysteine residue, via a disulfide bond. Furthermore, physicochemical properties of HP0377 and its R86A variant have been determined. These results suggest that HP0377 may perform multiple functions as a reductase in H. pylori.
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Affiliation(s)
- Ji Young Yoon
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 151-742, Republic of Korea
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9
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Roos G, Foloppe N, Messens J. Understanding the pK(a) of redox cysteines: the key role of hydrogen bonding. Antioxid Redox Signal 2013; 18:94-127. [PMID: 22746677 DOI: 10.1089/ars.2012.4521] [Citation(s) in RCA: 168] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Many cellular functions involve cysteine chemistry via thiol-disulfide exchange pathways. The nucleophilic cysteines of the enzymes involved are activated as thiolate. A thiolate is much more reactive than a neutral thiol. Therefore, determining and understanding the pK(a)s of functional cysteines are important aspects of biochemistry and molecular biology with direct implications for redox signaling. Here, we describe the experimental and theoretical methods to determine cysteine pK(a) values, and we examine the factors that control these pK(a)s. Drawing largely on experience gained with the thioredoxin superfamily, we examine the roles of solvation, charge-charge, helix macrodipole, and hydrogen bonding interactions as pK(a)-modulating factors. The contributions of these factors in influencing cysteine pK(a)s and the associated chemistry, including the relevance for the reaction kinetics and thermodynamics, are discussed. This analysis highlights the critical role of direct hydrogen bonding to the cysteine sulfur as a key factor modulating the equilibrium between thiol S-H and thiolate S(-). This role is easily understood intuitively and provides a framework for biochemical functional insights.
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Affiliation(s)
- Goedele Roos
- General Chemistry, Vrije University Brussel, Brussels, Belgium
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10
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Tang GW, Altman RB. Remote thioredoxin recognition using evolutionary conservation and structural dynamics. Structure 2011; 19:461-70. [PMID: 21481770 DOI: 10.1016/j.str.2011.02.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2010] [Revised: 02/06/2011] [Accepted: 02/16/2011] [Indexed: 12/25/2022]
Abstract
The thioredoxin family of oxidoreductases plays an important role in redox signaling and control of protein function. Not only are thioredoxins linked to a variety of disorders, but their stable structure has also seen application in protein engineering. Both sequence-based and structure-based tools exist for thioredoxin identification, but remote homolog detection remains a challenge. We developed a thioredoxin predictor using the approach of integrating sequence with structural information. We combined a sequence-based Hidden Markov Model (HMM) with a molecular dynamics enhanced structure-based recognition method (dynamic FEATURE, DF). This hybrid method (HMMDF) has high precision and recall (0.90 and 0.95, respectively) compared with HMM (0.92 and 0.87, respectively) and DF (0.82 and 0.97, respectively). Dynamic FEATURE is sensitive but struggles to resolve closely related protein families, while HMM identifies these evolutionary differences by compromising sensitivity. Our method applied to structural genomics targets makes a strong prediction of a novel thioredoxin.
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Affiliation(s)
- Grace W Tang
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
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11
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Abstract
The identification of protein disulfide isomerase, almost 50 years ago, opened the way to the study of oxidative protein folding. Oxidative protein folding refers to the composite process by which a protein recovers both its native structure and its native disulfide bonds. Pathways that form disulfide bonds have now been unraveled in the bacterial periplasm (disulfide bond protein A [DsbA], DsbB, DsbC, DsbG, and DsbD), the endoplasmic reticulum (protein disulfide isomerase and Ero1), and the mitochondrial intermembrane space (Mia40 and Erv1). This review summarizes the current knowledge on disulfide bond formation in both prokaryotes and eukaryotes and highlights the major problems that remain to be solved.
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Affiliation(s)
- Matthieu Depuydt
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium
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12
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Mavridou DAI, Saridakis E, Kritsiligkou P, Goddard AD, Stevens JM, Ferguson SJ, Redfield C. Oxidation state-dependent protein-protein interactions in disulfide cascades. J Biol Chem 2011; 286:24943-56. [PMID: 21543317 PMCID: PMC3137068 DOI: 10.1074/jbc.m111.236141] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Bacterial growth and pathogenicity depend on the correct formation of disulfide bonds, a process controlled by the Dsb system in the periplasm of Gram-negative bacteria. Proteins with a thioredoxin fold play a central role in this process. A general feature of thiol-disulfide exchange reactions is the need to avoid a long lived product complex between protein partners. We use a multidisciplinary approach, involving NMR, x-ray crystallography, surface plasmon resonance, mutagenesis, and in vivo experiments, to investigate the interaction between the two soluble domains of the transmembrane reductant conductor DsbD. Our results show oxidation state-dependent affinities between these two domains. These observations have implications for the interactions of the ubiquitous thioredoxin-like proteins with their substrates, provide insight into the key role played by a unique redox partner with an immunoglobulin fold, and are of general importance for oxidative protein-folding pathways in all organisms.
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Affiliation(s)
- Despoina A I Mavridou
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
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13
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Oxidoreductase activity of oligosaccharyltransferase subunits Ost3p and Ost6p defines site-specific glycosylation efficiency. Proc Natl Acad Sci U S A 2009; 106:11061-6. [PMID: 19549845 DOI: 10.1073/pnas.0812515106] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Asparagine-linked glycosylation is a common posttranslational modification of diverse secretory and membrane proteins in eukaryotes, where it is catalyzed by the multiprotein complex oligosaccharyltransferase. The functions of the protein subunits of oligoasccharyltransferase, apart from the catalytic Stt3p, are ill defined. Here we describe functional and structural investigations of the Ost3/6p components of the yeast enzyme. Genetic, biochemical and structural analyses of the lumenal domain of Ost6p revealed oxidoreductase activity mediated by a thioredoxin-like fold with a distinctive active-site loop that changed conformation with redox state. We found that mutation of the active-site cysteine residues of Ost6p and its paralogue Ost3p affected the glycosylation efficiency of a subset of glycosylation sites. Our results show that eukaryotic oligosaccharyltransferase is a multifunctional enzyme that acts at the crossroads of protein modification and protein folding.
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14
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Avoidance of the cytochrome c biogenesis system by periplasmic CXXCH motifs. Biochem Soc Trans 2008; 36:1124-8. [DOI: 10.1042/bst0361124] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The CXXCH motif is usually recognized in the bacterial periplasm as a haem attachment site in apocytochromes c. There is evidence that the Escherichia coli Ccm (cytochrome c maturation) system recognizes little more than the CXXCH sequence. A limited number of periplasmic proteins have this motif and yet are not c-type cytochromes. To explore how unwanted haem attachment to CXXCH might be avoided, and to determine whether haem attachment to the surface of a non-cytochrome protein would be possible, we converted the active-site CXXCK motif of a thioredoxin-like protein into CXXCH, the C-terminal domain of the transmembrane oxidoreductase DsbD (cDsbD). The E. coli Ccm system was found to catalyse haem attachment to a very small percentage of the resultant protein (∼0.2%). We argue that cDsbD folds sufficiently rapidly that only a small fraction fails to avoid the Ccm system, in contrast with bona fide c-type cytochromes that only adopt their tertiary structure following haem attachment. We also demonstrate covalent haem attachment at a low level in vivo to the periplasmic disulfide isomerase DsbC, which contains a native CXXCH motif. These observations provide insight into substrate recognition by the Ccm system and expand our understanding of the requirements for covalent haem attachment to proteins. The possible evolutionary relationship between thioredoxins and c-type cytochromes is discussed.
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15
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Mavridou DAI, Stevens JM, Goddard AD, Willis AC, Ferguson SJ, Redfield C. Control of periplasmic interdomain thiol:disulfide exchange in the transmembrane oxidoreductase DsbD. J Biol Chem 2008; 284:3219-3226. [PMID: 19004826 PMCID: PMC2631958 DOI: 10.1074/jbc.m805963200] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The bacterial protein DsbD transfers reductant from the cytoplasm to the
otherwise oxidizing environment of the periplasm. This reducing power is
required for several essential pathways, including disulfide bond formation
and cytochrome c maturation. DsbD includes a transmembrane domain
(tmDsbD) flanked by two globular periplasmic domains (nDsbD/cDsbD); each
contains a cysteine pair involved in electron transfer via a disulfide
exchange cascade. The final step in the cascade involves reduction of the
Cys103-Cys109 disulfide of nDsbD by Cys461 of
cDsbD. Here we show that a complex between the globular periplasmic domains is
trapped in vivo only when both are linked by tmDsbD. We have found
previously (Mavridou, D. A., Stevens, J. M., Ferguson, S. J.,
& Redfield, C. (2007) J. Mol. Biol.370
,643
-65817544440) that the attacking
cysteine (Cys461) in isolated cDsbD has a high
pKa value (10.5) that makes this thiol relatively
unreactive toward the target disulfide in nDsbD. Here we show using NMR that
active-site pKa values change significantly when cDsbD
forms a complex with nDsbD. This modulation of pKa values
is critical for the specificity and function of cDsbD. Uncomplexed cDsbD is a
poor nucleophile, allowing it to avoid nonspecific reoxidation; however, in
complex with nDsbD, the nucleophilicity of cDsbD increases permitting
reductant transfer. The observation of significant changes in active-site
pKa values upon complex formation has wider implications
for understanding reactivity in thiol:disulfide oxidoreductases.
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Affiliation(s)
- Despoina A I Mavridou
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Julie M Stevens
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Alan D Goddard
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Antony C Willis
- Medical Research Council Immunochemistry Unit, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Stuart J Ferguson
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
| | - Christina Redfield
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
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16
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Narzi D, Siu SWI, Stirnimann CU, Grimshaw JPA, Glockshuber R, Capitani G, Böckmann RA. Evidence for proton shuffling in a thioredoxin-like protein during catalysis. J Mol Biol 2008; 382:978-86. [PMID: 18692066 DOI: 10.1016/j.jmb.2008.07.061] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Revised: 07/21/2008] [Accepted: 07/22/2008] [Indexed: 10/21/2022]
Abstract
Proteins of the thioredoxin (Trx) superfamily catalyze disulfide-bond formation, reduction and isomerization in substrate proteins both in prokaryotic and in eukaryotic cells. All members of the Trx family with thiol-disulfide oxidoreductase activity contain the characteristic Cys-X-X-Cys motif in their active site. Here, using Poisson-Boltzmann-based protonation-state calculations based on 100-ns molecular dynamics simulations, we investigate the catalytic mechanism of DsbL, the most oxidizing Trx-like protein known to date. We observed several correlated transitions in the protonation states of the buried active-site cysteine and a neighboring lysine coupled to the exposure of the active-site thiolate. These results support the view of an internal proton shuffling mechanism during oxidation crucial for the uptake of two electrons from the substrate protein. Intramolecular disulfide-bond formation is probably steered by the conformational switch facilitating interaction with the active-site thiolate. A consistent catalytic mechanism for DsbL, probably conferrable to other proteins of the same class, is presented. Our results suggest a functional role of hydration entropy of active-site groups.
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Affiliation(s)
- Daniele Narzi
- Theoretical and Computational Membrane Biology, Center for Bioinformatics, Saarland University, Box 15 11 50, D-66041 Saarbrücken, Germany
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17
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Berkholz DS, Faber HR, Savvides SN, Karplus PA. Catalytic cycle of human glutathione reductase near 1 A resolution. J Mol Biol 2008; 382:371-84. [PMID: 18638483 DOI: 10.1016/j.jmb.2008.06.083] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Revised: 06/08/2008] [Accepted: 06/26/2008] [Indexed: 11/17/2022]
Abstract
Efficient enzyme catalysis depends on exquisite details of structure beyond those resolvable in typical medium- and high-resolution crystallographic analyses. Here we report synchrotron-based cryocrystallographic studies of natural substrate complexes of the flavoenzyme human glutathione reductase (GR) at nominal resolutions between 1.1 and 0.95 A that reveal new aspects of its mechanism. Compression in the active site causes overlapping van der Waals radii and distortion in the nicotinamide ring of the NADPH substrate, which enhances catalysis via stereoelectronic effects. The bound NADPH and redox-active disulfide are positioned optimally on opposite sides of the flavin for a 1,2-addition across a flavin double bond. The new structures extend earlier observations to reveal that the redox-active disulfide loop in GR is an extreme case of sequential peptide bonds systematically deviating from planarity--a net deviation of 53 degrees across five residues. But this apparent strain is not a factor in catalysis, as it is present in both oxidized and reduced structures. Intriguingly, the flavin bond lengths in oxidized GR are intermediate between those expected for oxidized and reduced flavin, but we present evidence that this may not be due to the protein environment but instead due to partial synchrotron reduction of the flavin by the synchrotron beam. Finally, of more general relevance, we present evidence that the structures of synchrotron-reduced disulfide bonds cannot generally be used as reliable models for naturally reduced disulfide bonds.
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Affiliation(s)
- Donald S Berkholz
- Department of Biochemistry and Biophysics, Oregon State University, 2011 ALS, Corvallis, OR 97331-7305, USA
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18
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Thermodynamic Aspects of DsbD-Mediated Electron Transport. J Mol Biol 2008; 380:783-8. [DOI: 10.1016/j.jmb.2008.05.050] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2008] [Revised: 05/18/2008] [Accepted: 05/21/2008] [Indexed: 01/23/2023]
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19
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Quinternet M, Selme L, Beaufils C, Tsan P, Jacob C, Boschi-Muller S, Averlant-Petit MC, Branlant G, Cung MT. 1H, 13C, and 15N resonance assignment of the C103S mutant of the N-terminal domain of DsbD from Neisseria meningitidis. BIOMOLECULAR NMR ASSIGNMENTS 2008; 2:85-87. [PMID: 19636931 DOI: 10.1007/s12104-008-9091-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Accepted: 03/31/2008] [Indexed: 05/28/2023]
Abstract
We report the nearly complete 1H, 13C, and 15N resonance assignments of the C103S mutant of the N-terminal domain of DsbD from Neisseria meningitides. Secondary structure determination using CSI method leads to the prediction of nine beta-sheet parts.
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Affiliation(s)
- Marc Quinternet
- Laboratoire de Chimie-Physique Macromoléculaire, UMR 7568 CNRS-INPL, Nancy-Université, 1 Rue Grandville, B.P. 20451, 54001 Nancy Cedex, France
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20
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Maeda K, Hägglund P, Finnie C, Svensson B, Henriksen A. Crystal structures of barley thioredoxin h isoforms HvTrxh1 and HvTrxh2 reveal features involved in protein recognition and possibly in discriminating the isoform specificity. Protein Sci 2008; 17:1015-24. [PMID: 18424513 DOI: 10.1110/ps.083460308] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
H-type thioredoxins (Trxs) constitute a particularly large Trx sub-group in higher plants. Here, the crystal structures are determined for the two barley Trx h isoforms, HvTrxh1 and HvTrxh2, in the partially radiation-reduced state to resolutions of 1.7 A, and for HvTrxh2 in the oxidized state to 2.0 A. The two Trxs have a sequence identity of 51% and highly similar fold and active-site architecture. Interestingly, the four independent molecules in the crystals of HvTrxh1 form two relatively large and essentially identical protein-protein interfaces. In each interface, a loop segment of one HvTrxh1 molecule is positioned along a shallow hydrophobic groove at the primary nucleophile Cys40 of another HvTrxh1 molecule. The association mode can serve as a model for the target protein recognition by Trx, as it brings the Met82 Cgamma atom (gamma position as a disulfide sulfur) of the bound loop segment in the proximity of the Cys40 thiol. The interaction involves three characteristic backbone-backbone hydrogen bonds in an antiparallel beta-sheet-like arrangement, similar to the arrangement observed in the structure of an engineered, covalently bound complex between Trx and a substrate protein, as reported by Maeda et al. in an earlier paper. The occurrence of an intermolecular salt bridge between Glu80 of the bound loop segment and Arg101 near the hydrophobic groove suggests that charge complementarity plays a role in the specificity of Trx. In HvTrxh2, isoleucine corresponds to this arginine, which emphasizes the potential for specificity differences between the coexisting barley Trx isoforms.
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Affiliation(s)
- Kenji Maeda
- Enzyme and Protein Chemistry, Department of Systems Biology, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
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21
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Ito K, Inaba K. The disulfide bond formation (Dsb) system. Curr Opin Struct Biol 2008; 18:450-8. [PMID: 18406599 DOI: 10.1016/j.sbi.2008.02.002] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2008] [Accepted: 02/29/2008] [Indexed: 11/16/2022]
Abstract
In oxidative folding of proteins in the bacterial periplasmic space, disulfide bonds are introduced by the oxidation system and isomerized by the reduction system. These systems utilize the oxidizing and the reducing equivalents of quinone and NADPH, respectively, that are transmitted across the cytoplasmic membrane through integral membrane components DsbB and DsbD. In both pathways, alternating interactions between a Cys-XX-Cys-containing thioredoxin domain and other regulatory domain lead to the maintenance of oxidized and reduced states of the specific terminal enzymes, DsbA that oxidizes target cysteines and DsbC that reduces an incorrect disulfide to allow its isomerization into the physiological one. Molecular details of these remarkable biochemical cascades are being rapidly unraveled by genetic, biochemical, and structural analyses in recent years.
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Affiliation(s)
- Koreaki Ito
- Institute for Virus Research, Kyoto University, Kyoto, Japan.
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22
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Vlamis-Gardikas A. The multiple functions of the thiol-based electron flow pathways of Escherichia coli: Eternal concepts revisited. Biochim Biophys Acta Gen Subj 2008; 1780:1170-200. [PMID: 18423382 DOI: 10.1016/j.bbagen.2008.03.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2007] [Revised: 03/18/2008] [Accepted: 03/22/2008] [Indexed: 10/22/2022]
Abstract
Electron flow via thiols is a theme with many variations in all kingdoms of life. The favourable physichochemical properties of the redox active couple of two cysteines placed in the optimised environment of the thioredoxin fold allow for two electron transfers in between top biological reductants and ultimate oxidants. The reduction of ribonucleotide reductases by thioredoxin and thioredoxin reductase of Escherichia coli (E. coli) was one of the first pathways to be elucidated. Diverse functions such as protein folding in the periplasm, maturation of respiratory enzymes, detoxification of hydrogen peroxide and prevention of oxidative damage may be based on two electron transfers via thiols. A growing field is the relation of thiol reducing pathways and the interaction of E. coli with different organisms. This concept combined with the sequencing of the genomes of different bacteria may allow for the identification of fine differences in the systems employing thiols for electron flow between pathogens and their corresponding mammalian hosts. The emerging possibility is the development of novel antibiotics.
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Affiliation(s)
- Alexios Vlamis-Gardikas
- Center of Basic Research I-Biochemistry Division, Biomedical Research Foundation (BRFAA), Academy of Athens, Soranou Efessiou 4, GR-11527 Athens, Greece.
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23
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Heras B, Kurz M, Shouldice SR, Martin JL. The name's bond……disulfide bond. Curr Opin Struct Biol 2007; 17:691-8. [DOI: 10.1016/j.sbi.2007.08.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2007] [Revised: 08/10/2007] [Accepted: 08/11/2007] [Indexed: 10/22/2022]
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24
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Mavridou DAI, Stevens JM, Ferguson SJ, Redfield C. Active-site Properties of the Oxidized and Reduced C-terminal Domain of DsbD Obtained by NMR Spectroscopy. J Mol Biol 2007; 370:643-58. [PMID: 17544440 DOI: 10.1016/j.jmb.2007.04.038] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2006] [Revised: 04/13/2007] [Accepted: 04/16/2007] [Indexed: 10/23/2022]
Abstract
The periplasmic C-terminal domain of the Escherichia coli DsbD protein (cDsbD) has a thioredoxin fold. The two cysteine residues in the CXXC motif serve as the reductant for the disulfide bond of the N-terminal domain which can in turn act as a reductant for various periplasmic partners. The resulting disulfide bond in cDsbD is reduced via an unknown mechanism by the transmembrane helical domain of the protein. We show by NMR analysis of (13)C, (15)N-labelled cDsbD that the protein is rigid, is stable to extremes of pH and undergoes only localized conformational changes in the vicinity of the CXXC motif, and in adjacent regions of secondary structure, upon undergoing the reduced/oxidized transition. pK(a) values have been determined, using 2D NMR, for the N-terminal cysteine of the CXXC motif, Cys461, as well as for other active-site residues. It is demonstrated using site-directed mutagenesis that the negative charges of the side-chains of Asp455 and Glu468 in the active site contribute to the unusually high pK(a) value, 10.5, of Cys461. This value is higher than expected from knowledge of the reduction potential of cDsbD. In a double mutant of cDsbD, D455N/E468Q, the pK(a) value of Cys461 is lowered to 8.6, a value close to that expected for an unperturbed cysteine residue. The pK(a) value of the second cysteine in wild-type cDsbD, Cys464, is significantly higher than the maximum pH value that was studied (pH 12.2).
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Affiliation(s)
- Despoina A I Mavridou
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
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25
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Rozhkova A, Glockshuber R. Kinetics of the intramolecular disulfide exchange between the periplasmic domains of DsbD. J Mol Biol 2006; 367:1162-70. [PMID: 17303162 DOI: 10.1016/j.jmb.2006.12.033] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2006] [Revised: 12/08/2006] [Accepted: 12/13/2006] [Indexed: 10/23/2022]
Abstract
DsbD from Escherichia coli catalyzes the transport of electrons from cytoplasmic thioredoxin to the periplasmic substrate proteins DsbC, DsbG and CcmG. DsbD consists of a periplasmic, N-terminal domain (nDsbD), a central transmembrane domain and a periplasmic, C-terminal domain (cDsbD). Each of these domains contains two essential cysteine residues that are required for intermolecular disulfide exchange between DsbD and substrates, and intramolecular disulfide exchange between the three DsbD domains. In order to determine the rate of intramolecular electron transfer from cDsbD to nDsbD, we constructed a redox-sensitive tryptophan variant of cDsbD (cDsbD(W)) that shows an approximately threefold increase in fluorescence upon reduction and has the same redox potential and reactivity as wild-type cDsbD. cDsbD(W) was then used for the construction of fusion proteins with nDsbD and cDsbD(W), connected via flexible linkers of different length. Using the DsbD substrate DsbC, which can only be reduced by nDsbD and does not react with cDsbD, we could directly measure the intramolecular electron transfer from cDsnD(W) to nDsbB in the fusion proteins. We show that the intramolecular disulfide exchange is significantly faster than the reaction between isolated nDsbD and cDsbD. Nevertheless, the effective concentration of 0.2 mM of the domains in the fusions is comaparably low. The rate of 23 s(-1) for the intramolecular disulfide exchange in the fusions was independent of the linker length and may represent the upper limit for the substrate turnover of full-length DsbD.
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Affiliation(s)
- Anna Rozhkova
- Institute of Molecular Biology and Biophysics, ETH Zurich 8093, Switzerland
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26
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Lewin A, Crow A, Oubrie A, Le Brun NE. Molecular Basis for Specificity of the Extracytoplasmic Thioredoxin ResA. J Biol Chem 2006; 281:35467-77. [PMID: 16971393 DOI: 10.1074/jbc.m607047200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ResA, an extracytoplasmic thioredoxin from Bacillus subtilis, acts in cytochrome c maturation by reducing the disulfide bond present in apocytochromes prior to covalent attachment of heme. This reaction is (and has to be) specific, as broad substrate specificity would result in unproductive shortcircuiting with the general oxidizing thioredoxin(s) present in the same compartment. Using mutational analysis and subsequent biochemical and structural characterization of active site variants, we show that reduced ResA displays unusually low reactivity at neutral pH, consistent with the observed high pKa values>8 for both active site cysteines. Residue Glu80 is shown to play a key role in controlling the acid-base properties of the active site. A model in which substrate binding dramatically enhances the reactivity of the active site cysteines is proposed to account for the specificity of the protein. Such a substratemediated activation mechanism is likely to have wide relevance for extracytoplasmic thioredoxins.
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Affiliation(s)
- Allison Lewin
- School of Chemical Sciences and Pharmacy, Centre for Metalloprotein Spectroscopy and Biology, University of East Anglia, Norwich NR4 7TJ, United Kingdom
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