Purification and amino acid sequence of lactocin S, a bacteriocin produced by Lactobacillus sake L45.
Lactocin S, a bacteriocin produced by Lactobacillus sake L45, has been purified to homogeneity by ion exchange, hydrophobic interaction and reverse-phase chromatography, and gel filtration. The purification resulted in approximately a 40,000-fold increase in the specific activity of lactocin S and enabled the determination of a major part of the amino acid sequence. Judging from the amino acid composition, lactocin S contained approximately 33 amino acid residues, of which about 50% were the nonpolar amino acids alanine, valine, and leucine. Amino acids were not detected upon direct N-terminal sequencing, indicating that the N-terminal amino acid was blocked. By cyanogen bromide cleavage at an internal methionine, the sequence of the 25 amino acids (including the methionine at the cleavage site) in the C-terminal part of the molecule was determined. The sequence was Met-Glu-Leu-Leu-Pro-Thr-Ala-Ala-Val-Leu-Tyr-Xaa-Asp-Val-Ala-Gly-Xaa-Phe- Lys-Tyr-Xaa-Ala-Lys-His-His, where Xaa represents unidentified residues. It is likely that the unidentified residues are modified forms of cysteine or amino acids associated with cysteine, since two cysteic acids per lactocin S molecule were found upon performic acid oxidation of lactocin S. The sequence was unique when compared to the SWISS-PROT data bank.
Mørtvedt
C I
CI
Norwegian Food Research Institute, Oslo.
Nissen-Meyer
J
J
Sletten
K
K
Nes
I F
IF
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001430:Bacteriocins / Q000737:chemistry / Q000302:isolation & purification*; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D007778:Lactobacillus / Q000032:analysis*; D008969:Molecular Sequence Data
D000596:Amino Acids; D001430:Bacteriocins; C035728:lactocin