title: The virulence factor PEB4 (Cj0596) and the periplasmic protein Cj1289 are two structurally related SurA-like chaperones in the human pathogen Campylobacter jejuni.
abstract: The PEB4 protein is an antigenic virulence factor implicated in host cell adhesion, invasion, and colonization in the food-borne pathogen Campylobacter jejuni. peb4 mutants have defects in outer membrane protein assembly and PEB4 is thought to act as a periplasmic chaperone. The crystallographic structure of PEB4 at 2.2-Å resolution reveals a dimer with distinct SurA-like chaperone and peptidyl-prolyl cis/trans isomerase (PPIase) domains encasing a large central cavity. Unlike SurA, the chaperone domain is formed by interlocking helices from each monomer, creating a domain-swapped architecture. PEB4 stimulated the rate of proline isomerization limited refolding of denatured RNase T(1) in a juglone-sensitive manner, consistent with parvulin-like PPIase domains. Refolding and aggregation of denatured rhodanese was significantly retarded in the presence of PEB4 or of an engineered variant specifically lacking the PPIase domain, suggesting the chaperone domain possesses a holdase activity. Using bioinformatics approaches, we identified two other SurA-like proteins (Cj1289 and Cj0694) in C. jejuni. The 2.3-Å structure of Cj1289 does not have the domain-swapped architecture of PEB4 and thus more resembles SurA. Purified Cj1289 also enhanced RNase T(1) refolding, although poorly compared with PEB4, but did not retard the refolding of denatured rhodanese. Structurally, Cj1289 is the most similar protein to SurA in C. jejuni, whereas PEB4 has most structural similarity to the Par27 protein of Bordetella pertussis. Our analysis predicts that Cj0694 is equivalent to the membrane-anchored chaperone PpiD. These results provide the first structural insights into the periplasmic assembly of outer membrane proteins in C. jejuni.
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom.
authors.forename: Avinash
authors.initials: A
authors.lastname: Kale
authors.forename: Chatchawal
authors.initials: C
authors.lastname: Phansopa
authors.forename: Chatrudee
authors.initials: C
authors.lastname: Suwannachart
authors.forename: C Jeremy
authors.initials: CJ
authors.lastname: Craven
authors.forename: John B
authors.initials: JB
authors.lastname: Rafferty
authors.forename: David J
authors.initials: DJ
authors.lastname: Kelly
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D016123:Campylobacter jejuni / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry*; D018833:Chaperonins / Q000737:chemistry; D018360:Crystallography, X-Ray / Q000379:methods; D029968:Escherichia coli Proteins / Q000737:chemistry*; D016680:Genome, Bacterial; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D018832:Molecular Chaperones / Q000235:genetics / Q000502:physiology*; D019696:Peptidylprolyl Isomerase / Q000737:chemistry*; D010957:Plasmids / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D013499:Surface Properties; D013884:Thiosulfate Sulfurtransferase / Q000737:chemistry; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; C560628:Cj0596 protein, Campylobacter jejuni; C560629:Cj1289 protein, Campylobacter jejuni; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D037521:Virulence Factors; D013884:Thiosulfate Sulfurtransferase; D018833:Chaperonins; C490900:SurA protein, E coli; D019696:Peptidylprolyl Isomerase