Sequence polymorphism, predicted secondary structures, and surface-exposedconformational epitopes of Campylobacter major outer membrane protein

The major outer membrane protein (MOMP), a putative porin and a multifuncti on surface protein of Campylobacter jejuni, may play an important role in t he adaptation of the organism to various host environments. To begin to dis sect the biological functions and antigenic features of this protein, the g ene (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 sing le-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 beta-strands connected by short peri plasmic turns and long irregular external loops. Alignment of the amino aci d 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, whi le the predicted beta-strands were formed by conserved sequences. The seque nce homology of cmp appeared to reflect the phylogenetic proximity of C. je juni strains, since strains with identical cmp sequences had indistinguisha ble or closely related macrorestriction fragment patterns. Using recombinan t 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.