Role of periplasmic chaperones and BamA (YaeT/Omp85) in folding and secretion of intimin from enteropathogenic Escherichia coli strains.
Intimin is a bacterial adhesin located on the surface of enteropathogenic Escherichia coli and other related bacteria that is believed to self-translocate across the outer membrane (OM), and therefore it has been regarded as a member of the type V secretion system (T5SS), which includes classical autotransporters (ATs). However, intimin has few structural similarities to classical ATs and an opposite topology with an OM-embedded N region and a secreted C region. Since the actual secretion mechanism of intimin is unknown, we investigated intimin biogenesis by analyzing its requirement of periplasmic chaperones (DsbA, SurA, Skp, and DegP) and of OM protein BamA (YaeT/Omp85) for folding, OM insertion, and translocation. Using full-length and truncated intimin polypeptides, we demonstrate that DsbA catalyzes the formation of a disulfide bond in the D3 lectin-like domain of intimin in the periplasm, indicating that this secreted C-terminal domain is at least partially folded prior to its translocation across the OM. We also show that SurA chaperone plays the major role for periplasmic transport and folding of the N region of intimin, whereas the parallel pathway made by Skp and DegP chaperones plays a secondary role in this process. Further, we demonstrate that BamA is essential for the insertion of the N region of intimin in the OM and that the protease activity of DegP participates in the degradation of misfolded intimin. The significance of these findings for a BamA-dependent secretion mechanism of intimin is discussed in the context of T5SSs.
Bodelón
Gustavo
G
Department of Microbial Biotechnology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Campus de Cantoblanco, 28049 Madrid, Spain.
Marín
Elvira
E
Fernández
Luis Angel
LA
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D054308:Enteropathogenic Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005434:Flow Cytometry; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009154:Mutation; D010447:Peptide Hydrolases / Q000378:metabolism; D019696:Peptidylprolyl Isomerase / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D019897:Periplasm / Q000378:metabolism*; D033903:Periplasmic Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D019704:Protein Disulfide-Isomerases / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D017510:Protein Folding; D021381:Protein Transport; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism / Q000502:physiology
D001425:Bacterial Outer Membrane Proteins; C503914:BamA protein, E coli; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D033903:Periplasmic Proteins; C072721:Skp protein, E coli; D010447:Peptide Hydrolases; C061682:DegP protease; D012697:Serine Endopeptidases; C490900:SurA protein, E coli; D019696:Peptidylprolyl Isomerase; D019704:Protein Disulfide-Isomerases; C526648:dsbA protein, E coli