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 foodborne 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.

Dimeric Structure of the Bacterial Extracellular Foldase PrsA

“…4D) and the attached parvulin domain may even permit adaptation to larger substrates. The only other chaperone with PPIase/NC domain architecture, for which dimerization and the formation of an enlarged crevice has been observed, is Peb4 from Campylobacter jejuni (13). However, its NC region is more distantly related to the SurA/trigger factor and dimerization under unusual domain swapping is required for completion of the NC-domain (25,26).…”

“…The N-terminal region of PrsA starts with a pair of short antiparallel ␤-strands (Val 9 -Thr 13 and Asp 16 -Thr 19 ) followed by five ␣-helices before entering the parvulin domain. The C-terminal region is arranged into two long ␣-helices that tightly interact with the N-terminal helices.…”

“…nitrogenase reductase (9) and various virulence factors (10,11). A network of periplasmic PPIases, including SurA, FkpA, CypB, and Par10, supports the folding of periplasmic and outer membrane proteins in Gram-negative bacteria (12,13). In Gram-positive bacteria, the parvulin-type PPIase PrsA is the only general factor mediating folding of secreted proteins, which are essential for bacterial pathogenicity and cell wall biosynthesis.…”

Transcriptional Profiling of Neisseria meningitidis Interacting with Human Epithelial Cells in a Long-Term In Vitro Colonization Model

“…The biological functions of these genes are unknown, except that NMB0345 is homologous to cj0596 from Campylobacter jejuni, encoding a protein known to be important for epithelial cell adherence, colonization of mouse intestinal epithelium, and biofilm formation (56). Further work will be required to ascertain whether specific genes in the NMB0342-NMB0348 locus have a role in outer membrane protein assembly, as was suggested for cj0596 (57), and in promoting epithelialbacterial cell interactions and/or colonization.…”

Bacterial N-Glycosylation Efficiency Is Dependent on the Structural Context of Target Sequons

“…Although the enzymes required to synthesize and transfer the C. jejuni heptasaccharide are encoded adjacent to each other on the chromosome, there may be other nonessential components elsewhere on the chromosome with analogous functions to the eukaryotic OTase subunits. One candidate protein is PpiD (peptidyl prolyl isomerase), which was recently identified in C. jejuni (64). The PpiD E. coli homolog is anchored in the inner membrane and interacts with SecYEG, modulating folding of newly exported proteins (65,66).…”