Characterization and gene sequencing of a 19-kDa periplasmic protein of Campylobacter jejuni/coli

In order to study a 19-kDa protein (p19) of Campylobacter jejuni, we purified this protein to homogeneity from C. jejuni strain 81,176 by anion exchange chromatography. The molecular weight of the native protein is 19,000 daltons. P19 was found to be acidic with an isoelectric point of 4.8 and was located in the periplasmic space of the bacteria. The 20 N-terminal amino acids were sequenced and no significant similarities with known proteins were shown. A monoclonal antibody showed that p19 is conserved in the 2 species C. jejuni and C. coli. Analysis of sera from 23 patients with a Campylobacter-related infection indicated that p19 is not immunogenic during natural infection in man. The gene encoding p19 was cloned and no strong homologies with known sequences were identified. The preparation of a knockout mutant in p19 will enable the investigation of the function of this cell wall component of Campylobacter.