Sakacin g, a new type of antilisterial bacteriocin

Abstract

Sakacin G is a 37-amino-acid-residue-long class IIa bacteriocin produced by Lactobacillus sake 2512, which is encoded by the duplicated structural genes skgA1 and skgA2. Sakacin G appears to be unique and seems to be an intermediate between pediocin-like bacteriocins, according to its double-disulfide bridges required for antimicrobial activity, and mesentericin-like bacteriocins in terms of sequence homologies, inhibition spectrum, and specific activity.

FIG. 1.

Sequence alignment of class IIa bacteriocins. Leucocin A is identical to lecucocin B (12). Piscicocin V1a is identical to piscicolin 126 (19), sakacin A is identical to curvacin A (32), carnobacteriocin BM1 is identical to piscicocin V1b (6), and pediocin PA-1 is identical to pediocin AcH (26) and pediocin SJ-1 (30). Bavaracin A (21) is probably identical to sakacin P. Residues are numbered according to the sequence of sakacin G. The consensus sequence includes residues conserved by at least 75%. The residues conserved by more than 90% are underlined.

FIG. 2.

Schematic representation of the sequenced 2.1-kbp HindIII fragment isolated from plasmid pJMB35. A size bar (0.5 kbp) is shown in the upper left corner.

FIG. 3.

Sequence alignments and relevant features from the proteic sequences deduced from the skgA1 and skgA2 genes. Differences between the two sequences are framed.