MOLECULAR CHARACTERIZATION OF A CAMPYLOBACTER-JEJUNI LIPOPROTEIN WITH HOMOLOGY TO PERIPLASMIC SIDEROPHORE-BINDING PROTEINS

A genomic library of Campylobacter jejuni (NCTC 11351) was used to identify genes which could confer a hemolytic phenotype to Escherichia coli, Accordingly, when transformants were screened on blood plates, hemolytic colonies appeared at a frequency of 3 x 10(-4). The gene conferring the hemolytic activity was identified by subcloning and was found to be responsible for the phenotype of all hemolytic transformants isolated. The open reading frame conferring this activity encodes a protein of 36,244 Da with atypical endopeptidase type II leader sequence, The protein is modified with palmitic acid when it is processed in E. coli, confirming that it is a typical lipoprotein. The deduced gene product of 329 amino acids has significant homology to the group of solute binding proteins from periplasmic-binding-protein-dependent transport systems for ferric siderophores, including the FatB protein from Vibrio anguillarium and the FhuD protein from Bacillus subtilis. In particular, the protein contained the signature sequence for siderophore-binding proteins, suggesting that the protein may be the siderophore-binding protein component of an iron acquisition system of C. jejuni.