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Reardon-Robinson ME, Nguyen MT, Sanchez BC, Osipiuk J, Rückert C, Chang C, Chen B, Nagvekar R, Joachimiak A, Tauch A, Das A, Ton-That H. A cryptic oxidoreductase safeguards oxidative protein folding in Corynebacterium diphtheriae. Proc Natl Acad Sci U S A 2023; 120:e2208675120. [PMID: 36787356 PMCID: PMC9974433 DOI: 10.1073/pnas.2208675120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 01/17/2023] [Indexed: 02/15/2023] Open
Abstract
In many gram-positive Actinobacteria, including Actinomyces oris and Corynebacterium matruchotii, the conserved thiol-disulfide oxidoreductase MdbA that catalyzes oxidative folding of exported proteins is essential for bacterial viability by an unidentified mechanism. Intriguingly, in Corynebacterium diphtheriae, the deletion of mdbA blocks cell growth only at 37 °C but not at 30 °C, suggesting the presence of alternative oxidoreductase enzyme(s). By isolating spontaneous thermotolerant revertants of the mdbA mutant at 37 °C, we obtained genetic suppressors, all mapped to a single T-to-G mutation within the promoter region of tsdA, causing its elevated expression. Strikingly, increased expression of tsdA-via suppressor mutations or a constitutive promoter-rescues the pilus assembly and toxin production defects of this mutant, hence compensating for the loss of mdbA. Structural, genetic, and biochemical analyses demonstrated TsdA is a membrane-tethered thiol-disulfide oxidoreductase with a conserved CxxC motif that can substitute for MdbA in mediating oxidative folding of pilin and toxin substrates. Together with our observation that tsdA expression is upregulated at nonpermissive temperature (40 °C) in wild-type cells, we posit that TsdA has evolved as a compensatory thiol-disulfide oxidoreductase that safeguards oxidative protein folding in C. diphtheriae against thermal stress.
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Affiliation(s)
- Melissa E. Reardon-Robinson
- Department of Microbiology & Molecular Genetics, University of Texas McGovern Medical School, Houston, TX77030
| | - Minh Tan Nguyen
- Division of Oral and Systemic Health Sciences, School of Dentistry, University of California, Los Angeles, CA90095
| | - Belkys C. Sanchez
- Department of Microbiology & Molecular Genetics, University of Texas McGovern Medical School, Houston, TX77030
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX77030
| | - Jerzy Osipiuk
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and Engineering, University of Chicago, Chicago, IL60637
- Structural Biology Center, Argonne National Laboratory, Lemont, IL60439
| | - Christian Rückert
- Center for Biotechnology, Bielefeld University, D-33615Bielefeld, Germany
| | - Chungyu Chang
- Division of Oral and Systemic Health Sciences, School of Dentistry, University of California, Los Angeles, CA90095
| | - Bo Chen
- Department of Microbiology & Molecular Genetics, University of Texas McGovern Medical School, Houston, TX77030
| | - Rahul Nagvekar
- Department of Microbiology & Molecular Genetics, University of Texas McGovern Medical School, Houston, TX77030
- Stanford University, Stanford, CA94305
| | - Andrzej Joachimiak
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and Engineering, University of Chicago, Chicago, IL60637
- Structural Biology Center, Argonne National Laboratory, Lemont, IL60439
| | - Andreas Tauch
- Center for Biotechnology, Bielefeld University, D-33615Bielefeld, Germany
| | - Asis Das
- Department of Medicine, Neag Comprehensive Cancer Center, University of Connecticut Health Center, Farmington, CT06030
| | - Hung Ton-That
- Division of Oral and Systemic Health Sciences, School of Dentistry, University of California, Los Angeles, CA90095
- Molecular Biology Institute, University of California, Los Angeles, CA90095
- Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles, CA90095
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Reardon-Robinson ME, Osipiuk J, Jooya N, Chang C, Joachimiak A, Das A, Ton-That H. A thiol-disulfide oxidoreductase of the Gram-positive pathogen Corynebacterium diphtheriae is essential for viability, pilus assembly, toxin production and virulence. Mol Microbiol 2015; 98:1037-50. [PMID: 26294390 DOI: 10.1111/mmi.13172] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2015] [Indexed: 12/19/2022]
Abstract
The Gram-positive pathogen Corynebacterium diphtheriae exports through the Sec apparatus many extracellular proteins that include the key virulence factors diphtheria toxin and the adhesive pili. How these proteins attain their native conformations after translocation as unfolded precursors remains elusive. The fact that the majority of these exported proteins contain multiple cysteine residues and that several membrane-bound oxidoreductases are encoded in the corynebacterial genome suggests the existence of an oxidative protein-folding pathway in this organism. Here we show that the shaft pilin SpaA harbors a disulfide bond in vivo and alanine substitution of these cysteines abrogates SpaA polymerization and leads to the secretion of degraded SpaA peptides. We then identified a thiol-disulfide oxidoreductase (MdbA), whose structure exhibits a conserved thioredoxin-like domain with a CPHC active site. Remarkably, deletion of mdbA results in a severe temperature-sensitive cell division phenotype. This mutant also fails to assemble pilus structures and is greatly defective in toxin production. Consistent with these defects, the ΔmdbA mutant is attenuated in a guinea pig model of diphtheritic toxemia. Given its diverse cellular functions in cell division, pilus assembly and toxin production, we propose that MdbA is a component of the general oxidative folding machine in C. diphtheriae.
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Affiliation(s)
- Melissa E Reardon-Robinson
- Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX, USA
| | - Jerzy Osipiuk
- Midwest Center for Structural Genomics, Department of Biosciences, Argonne National Laboratory, Argonne, IL, USA.,Structural Biology Center, Department of Biosciences, Argonne National Laboratory, Argonne, IL, USA
| | - Neda Jooya
- Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX, USA
| | - Chungyu Chang
- Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX, USA
| | - Andrzej Joachimiak
- Midwest Center for Structural Genomics, Department of Biosciences, Argonne National Laboratory, Argonne, IL, USA.,Structural Biology Center, Department of Biosciences, Argonne National Laboratory, Argonne, IL, USA
| | - Asis Das
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, USA
| | - Hung Ton-That
- Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX, USA
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Reardon-Robinson ME, Osipiuk J, Chang C, Wu C, Jooya N, Joachimiak A, Das A, Ton-That H. A Disulfide Bond-forming Machine Is Linked to the Sortase-mediated Pilus Assembly Pathway in the Gram-positive Bacterium Actinomyces oris. J Biol Chem 2015; 290:21393-405. [PMID: 26170452 PMCID: PMC4571867 DOI: 10.1074/jbc.m115.672253] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Indexed: 12/30/2022] Open
Abstract
Export of cell surface pilins in Gram-positive bacteria likely occurs by the translocation of unfolded precursor polypeptides; however, how the unfolded pilins gain their native conformation is presently unknown. Here, we present physiological studies to demonstrate that the FimA pilin of Actinomyces oris contains two disulfide bonds. Alanine substitution of cysteine residues forming the C-terminal disulfide bridge abrogates pilus assembly, in turn eliminating biofilm formation and polymicrobial interaction. Transposon mutagenesis of A. oris yielded a mutant defective in adherence to Streptococcus oralis, and revealed the essential role of a vitamin K epoxide reductase (VKOR) gene in pilus assembly. Targeted deletion of vkor results in the same defects, which are rescued by ectopic expression of VKOR, but not a mutant containing an alanine substitution in its conserved CXXC motif. Depletion of mdbA, which encodes a membrane-bound thiol-disulfide oxidoreductase, abrogates pilus assembly and alters cell morphology. Remarkably, overexpression of MdbA or a counterpart from Corynebacterium diphtheriae, rescues the Δvkor mutant. By alkylation assays, we demonstrate that VKOR is required for MdbA reoxidation. Furthermore, crystallographic studies reveal that A. oris MdbA harbors a thioredoxin-like fold with the conserved CXXC active site. Consistently, each MdbA enzyme catalyzes proper disulfide bond formation within FimA in vitro that requires the catalytic CXXC motif. Because the majority of signal peptide-containing proteins encoded by A. oris possess multiple Cys residues, we propose that MdbA and VKOR constitute a major folding machine for the secretome of this organism. This oxidative protein folding pathway may be a common feature in Actinobacteria.
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Affiliation(s)
- Melissa E. Reardon-Robinson
- From the Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas 77030
| | - Jerzy Osipiuk
- the Department of Biosciences, Midwest Center for Structural Genomics, and ,the Department of Biosciences, Structural Biology Center, Argonne National Laboratory, Argonne, Illinois 60439, and
| | - Chungyu Chang
- From the Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas 77030
| | - Chenggang Wu
- From the Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas 77030
| | - Neda Jooya
- From the Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas 77030
| | - Andrzej Joachimiak
- the Department of Biosciences, Midwest Center for Structural Genomics, and ,the Department of Biosciences, Structural Biology Center, Argonne National Laboratory, Argonne, Illinois 60439, and
| | - Asis Das
- the Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Hung Ton-That
- From the Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas 77030,
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