The protein PEB1 (28 kDa) is a common antigen and a major cell adherence molecule of Campylobacter jejuni and Campylobacter coli. We created a bank of chromosomal DNA fragments of C. jejuni strain 81-176 using lambda gt11. Screening this bank in Escherichia coli Y1090 cells with antibody raised against purified PEB1 enabled us to isolate and to purify a clone with a 2.6-kilobase insert expressing an immunoreactive protein of 28 kDa. DNA sequencing revealed that the insert contains three complete and two partial open reading frames (ORFs), designated 5' to 3' as ORFs A-E. The peb1A gene (ORF D) contains 780 bases encoding a 259-residue polypeptide having a calculated molecular mass of 28,181 Da. The peptide sequence starting at residue 27 matches that determined from aminoterminal sequencing of mature PEB1 from C. jejuni. The first 26 residues contain typical signal peptidase I and II cleavage sites. The deduced amino acid composition and pI of the recombinant mature protein are similar to those determined for purified PEB1. Gene bank searches indicated significant overall homology of peb1A and ORF C with operons for amino acid transport systems in other Gram-negative organisms. peb1A is homologous to the binding components of systems such as glnH (27.8%) and hisJ (28.9%), whereas ORF C has nearly 50% identity to glnQ and hisP. Thus, PEB1 could be involved both in binding to intestinal cells and in amino acid transport.