title: Structural and functional differences in two cyclic bacteriocins with the same sequences produced by lactobacilli.
abstract: Lactobacillus gasseri LA39 and L. reuteri LA6 isolated from feces of the same human infant were found to produce similar cyclic bacteriocins (named gassericin A and reutericin 6, respectively) that cannot be distinguished by molecular weights or primary amino acid sequences. However, reutericin 6 has a narrower spectrum than gassericin A. In this study, gassericin A inhibited the growth of L. reuteri LA6, but reutericin 6 did not inhibit the growth of L. gasseri LA39. Both bacteriocins caused potassium ion efflux from indicator cells and liposomes, but the amounts of efflux and patterns of action were different. Although circular dichroism spectra of purified bacteriocins revealed that both antibacterial peptides are composed mainly of alpha-helices, the spectra of the bacteriocins did not coincide. The results of D- and L-amino acid composition analysis showed that two residues and one residue of D-Ala were detected among 18 Ala residues of gassericin A and reutericin 6, respectively. These findings suggest that the different D-alanine contents of the bacteriocins may cause the differences in modes of action, amounts of potassium ion efflux, and secondary structures. This is the first report that characteristics of native bacteriocins produced by wild lactobacillus strains having the same structural genes are influenced by a difference in D-amino acid contents in the molecules.
authors.affiliation: Laboratory of Animal Products Chemistry, Graduate School of Agricultural Science, Tohoku University, Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai 981-8555, Japan. ykawai@bios.tohoku.ac.jp
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kawai
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Ishii
authors.forename: Kensuke
authors.initials: K
authors.lastname: Arakawa
authors.forename: Koichiro
authors.initials: K
authors.lastname: Uemura
authors.forename: Boku
authors.initials: B
authors.lastname: Saitoh
authors.forename: Junko
authors.initials: J
authors.lastname: Nishimura
authors.forename: Haruki
authors.initials: H
authors.lastname: Kitazawa
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Yamazaki
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Tateno
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Itoh
authors.forename: Tadao
authors.initials: T
authors.lastname: Saito
mesh_terms: D000595:Amino Acid Sequence; D001430:Bacteriocins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D002942:Circular Dichroism; D005243:Feces / Q000382:microbiology; D006801:Humans; D007223:Infant; D007778:Lactobacillus / Q000187:drug effects / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D013329:Structure-Activity Relationship
chemical_list: D001430:Bacteriocins; C096679:gassericin A