Proteins of this family are found in Campylobacter jejuni and Campylobacter lari but not in Campylobacter coli, although the respective gene was detected in some cases in all three species by PCR. The protein shows a pore-forming activity, with cation selective channel properties. No significant similarity exists between omp50 and the members of the MOMP family of Campylobacter which is in agreement with the absence of antigenic cross-reactivity between these two proteins.