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Identification of membrane‐associated proteins from Campylobacter jejuni strains using complementary proteomics technologies

Campylobacter jejuni is the leading cause of food‐ and water‐borne illness world‐wide. The membrane‐associated proteome of a recent C. jejuni gastrointestinal isolate (JHH1) was generated by sodium carbonate precipitation and ultracentrifugation followed by 2‐DE and MALDI‐TOF MS as well as 2‐DLC (strong cation exchange followed by RP chromatography) of trypsin digests coupled to MS/MS (2‐DLC/MS/MS). 2‐DE/MS identified 77 proteins, 44 of which were predicted membrane proteins, while 2‐DLC/MS/MS identified 432 proteins, of which 206 were predicted to be membrane associated. A total of 453 unique proteins (27.4% of the C. jejuni theoretical proteome), including 187 bona fide membrane proteins were identified in this study. Membrane proteins were also compared between C. jejuni JHH1 and ATCC 700297 to identify factors potentially associated with increased gastrointestinal virulence. We identified 28 proteins that were significantly (>two‐fold) more abundant in, or unique to, JHH1, including eight proteins involved in chemotaxis signal transduction and flagellar motility, the amino acid‐binding surface antigens CjaA and CjaC, and four outer membrane proteins (OMPs) of unknown function (Cj0129c, Cj1031, Cj1279c, and Cj1721c). Immunoblotting using convalescent patient sera generated postgastrointestinal infection revealed 13 (JHH1) and 12 (ATCC 700297) immunoreactive proteins. These included flagellin (FlaA) and CadF as well as Omp18, Omp50, Cj1721c, PEB1A, PEB2, and PEB4A. This study provides a comprehensive analysis of membrane‐associated proteins from C. jejuni.