title: A thiol-disulfide oxidoreductase of the Gram-positive pathogen Corynebacterium diphtheriae is essential for viability, pilus assembly, toxin production and virulence.
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.
authors: Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX, USA.
authors: Melissa E
authors: ME
authors: Reardon-Robinson
authors: 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.
authors: Jerzy
authors: J
authors: Osipiuk
authors: Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX, USA.
authors: Neda
authors: N
authors: Jooya
authors: Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX, USA.
authors: Chungyu
authors: C
authors: Chang
authors: 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.
authors: Andrzej
authors: A
authors: Joachimiak
authors: Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, USA.
authors: Asis
authors: A
authors: Das
authors: Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX, USA.
authors: Hung
authors: H
authors: Ton-That
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D003353:Corynebacterium diphtheriae / Q000201:enzymology* / Q000472:pathogenicity* / Q000502:physiology; D004165:Diphtheria / Q000382:microbiology; D004167:Diphtheria Toxin / Q000096:biosynthesis / Q000097:blood; D036781:Fimbriae Proteins / Q000737:chemistry* / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000737:chemistry / Q000378:metabolism; D006168:Guinea Pigs; D050296:Microbial Viability; D009154:Mutation; D010641:Phenotype; D011490:Protein Disulfide Reductase (Glutathione) / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D017510:Protein Folding; D014115:Toxemia / Q000382:microbiology; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004167:Diphtheria Toxin; D036781:Fimbriae Proteins; D011490:Protein Disulfide Reductase (Glutathione)