Partial nucleotide sequences of the sapD and sapF genes of the sap operon (GenBank Accession No. AF178651) from Vibrio fischeri ATCC 7744 have been determined, and the peptide transport system of ATP-binding proteins SapD and SapF encoded by the genes have been deduced, Alignment and comparison of the Sap proteins of V. fischeri, Escherichia coli, Salmonella typhimurium, and Haemophilus influenzae Rd show that these proteins are homologous. The sap operon residing in the genome enables V. fischeri to transport peptides and resist antimicrobial peptides, Nucleotide sequence and functional analyses confirm that the specific regulatory-region-like sequence R&R* that resides inside the sapD gene and before the sapF gene functions in gene expression and regulation; also, it is regulated by the LuxR-AI complex of the V. fischeri lux regulon. The putative upstream activator binding sequences Sigma UASI, Sigma UASII, Sigma UASIII TGTCGACTTGGGCCTCGCTGTCCGTATGCACA (72nd to 103rd bp), TGTCCGTATGCACA (90th to 103rd bp), and TGTTCAAGTACCAGAAAGACA (111st to 133rd bp) in the R&R* sequence, which are similar to the two-component regulator binding sequence TGT-N8-12-ACA and the LuxR-AI binding sequence ACCTGTAGGATCGTACAGGT in the regulatory region of the V. fischeri lux regulon, might be the specific sequences recognized by the LuxR-AI complex for enhancement.