Jm. Bolla et al., Purification, characterization and sequence analysis of Omp50, a new porinisolated from Campylobacter jejuni, BIOCHEM J, 352, 2000, pp. 637-643
A novel pore-forming protein identified in Campylobacter was purified by io
n-exchange chromatography and named Omp50 according to both its molecular m
ass and its outer membrane localization. We observed a pore-forming ability
of Omp50 after re-incorporation into artificial membranes. The protein ind
uced cation-selective channels with major conductance values of 50-60 pS in
1 M NaCl. N-terminal sequencing allowed us to identify the predicted codin
g sequence Cj1170c from the Campylobacter jejuni genome database as the cor
responding gene in the NCTC 11168 genome sequence. The gene, designated omp
50, consists of a 1425 bp open reading frame encoding a deduced 453-amino a
cid protein with a calculated pI of 5.81 and a molecular mass of 51169.2 Da
. The protein possessed a 20-amino acid leader sequence. No significant sim
ilarity was found between Omp50 and porin protein sequences already determi
ned. Moreover, the protein showed only weak sequence identity with the majo
r outer-membrane protein (MOMP) of Campylobacter, correlating with the abse
nce of antigenic cross-reactivity between these two proteins. Omp50 is expr
essed in C. jejuni and Campylobacter lari but not in Campylobacter coli. Th
e gene, however, was detected in all three species by PCR. According to its
conformation and functional properties, the protein would belong to the fa
mily of outer-membrane monomeric porins.