Sequence Polymorphism, Predicted Secondary Structures, and Surface-Exposed Conformational Epitopes of Campylobacter Major Outer Membrane Protein

Abstract

The major outer membrane protein (MOMP), a putative porin and a multifunction surface protein of Campylobacter jejuni, may play an important role in the adaptation of the organism to various host environments. To begin to dissect the biological functions and antigenic features of this protein, the gene (designated cmp) encoding MOMP was identified and characterized from 22 strains of C. jejuni and one strain of C. coli. It was shown that the single-copy cmp locus encoded a protein with characteristics of bacterial outer membrane proteins. Prediction from deduced amino acid sequences suggested that each MOMP subunit consisted of 18 ␤-strands connected by short periplasmic turns and long irregular external loops. Alignment of the amino acid sequences of MOMP from different strains indicated that there were seven localized variable regions dispersed among highly conserved sequences. The variable regions were located in the putative external loop structures, while the predicted ␤-strands were formed by conserved sequences. The sequence homology of cmp appeared to reflect the phylogenetic proximity of C. jejuni strains, since strains with identical cmp sequences had indistinguishable or closely related macrorestriction fragment patterns. Using recombinant MOMP and antibodies recognizing linear or conformational epitopes of the protein, it was demonstrated that the surface-exposed epitopes of MOMP were predominantly conformational in nature. These findings are instrumental in the design of MOMP-based diagnostic tools and vaccines.

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

“…The trimer conformation, however, has been confirmed in two-dimensional crystallization studies (12,787). Primary sequence analysis utilizing local hydrophobicity and sequence divergence among isolates suggested the presence of 18, rather than 16, transmembrane ␤-strands (362,782), and comparison with specific channels LamB and ScrY (described below) showed potential conservation of some short signature motifs (362). On this basis, MOMP will be a specific channel rather than a general porin.…”

“…Porins from the organisms in the ε-proteobacteria, which forms a very deep branch almost reaching the bottom of the whole Proteobacteria group, are indeed quite different in sequence, and I have not been able to align porins from Helicobacter pylori (60,178,196) or Campylobacter jejuni (78,79,362,782) with the porin sequences shown in Fig. 1.…”

Point mutations in the major outer membrane protein drive hypervirulence of a rapidly expanding clone of Campylobacter jejuni

“…MOMP is the most abundant membrane protein in C. jejuni with 18 β-strands and nine external loops (23). The 18 aa differences between the porA alleles of NCTC11168 and IA3902 clustered preferentially on several of the nine surface-exposed loops (Fig.…”

Campylobacter sequence typing databases: applications and future prospects

“…Campylobacter AGST Additional discrimination of isolates, where required, has been achieved by indexing variation in the SVRs of the antigen genes flaA and flaB, encoding A and B regions of the flagella (Alm et al, 1993), and porA, encoding a major outer-membrane protein (Zhang et al, 2000). These can be sequence-typed in combination with MLST, for example to detect strains responsible for disease outbreaks (Clark et al, 2005;Dingle et al, 2002Dingle et al, , 2008Meinersmann et al, 1997;Sails et al, 2003a).…”