title: Elucidation of the structure of SA-FF22, a lanthionine-containing antibacterial peptide produced by Streptococcus pyogenes strain FF22.
abstract: The antibacterial peptide SA-FF22, produced by the pathogen Streptococcus pyogenes strain FF22 was purified and features of its primary and secondary structure were characterised. Mass spectrometry demonstrated the pure peptide had a mass of 2794Da while, amino acid analysis revealed the presence of the unusual, thioether amino acids lanthionine and 3-methyllanthionine; thus SA-FF22 is a member of the group of antibacterial polypeptides termed lantibiotics. Furthermore, amino acid sequencing showed a unique sequence which was blocked at position 23 by a residue of the unsaturated amino acid 2,3-didehydrobutyrine. Carboxypeptidase-Y digestion could be used to demonstrate that serine occupies the C-terminal position only after complete oxidation of the thioether amino acid bridges, suggesting that the three-dimensional structure of the native peptide may prevent access of the enzyme to the C-terminus. Fragmentation of the native peptide with a variety of proteolytic enzymes failed to yield a peptide containing less than all three of the cross-linked lanthionine and methyllanthionine residues and demonstrated that all three thioether bridges overlapped. Analysis of the circular dichroism of SA-FF22 in various concentrations of 2,2,2-trifluoroethanol in water, SDS micelles and in the presence of artificial phospholipid vesicles suggested that there is significant change in its secondary structure from aqueous to lipophilic environments.
authors.affiliation: Department of Microbiology, University of Otago, Dunedin, New Zealand.
authors.forename: R W
authors.initials: RW
authors.lastname: Jack
authors.forename: A
authors.initials: A
authors.lastname: Carne
authors.forename: J
authors.initials: J
authors.lastname: Metzger
authors.forename: S
authors.initials: S
authors.lastname: Stefanović
authors.forename: H G
authors.initials: HG
authors.lastname: Sahl
authors.forename: G
authors.initials: G
authors.lastname: Jung
authors.forename: J
authors.initials: J
authors.lastname: Tagg
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives* / Q000032:analysis; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000900:Anti-Bacterial Agents / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D001430:Bacteriocins; D002942:Circular Dichroism; D010450:Endopeptidases; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D010455:Peptides; D017433:Protein Structure, Secondary; D013297:Streptococcus pyogenes / Q000378:metabolism*; D013440:Sulfides
chemical_list: D000596:Amino Acids; D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D010446:Peptide Fragments; D010455:Peptides; D013440:Sulfides; C016887:A-FF22; D010450:Endopeptidases; C001520:lanthionine; D000409:Alanine