Pediococcus sp. ISK-1 produces a novel lantibiotic, bacteriocin ISK-1

Bacteriocin ISK-1 is a proteinaceous inhibitory substance produced by Pedio coccus sp. ISK-1 isolated from well-aged Nukadoko (Kimura et al., 1997a). B acteriocin ISK-1 was purified by acid treatment, ammonium sulfate precipita tion, cation-exchange chromatography and reversed-phase high performance ch romatography from the culture supernatant of Pediococcus sp. ISK-1. Purific ation of bacteriocin ISK-1 resulted in 30-fold increase in the specific act ivity and the recovery was 17%. Molecular mass of bacteriocin ISK-1 determi ned by fast atom bombardment-mass spectrometry was 2,960. The amino acid co mposition analysis of bacteriocin ISK-1 revealed that it contained lanthion ine and/or 3-methyllanthionine which is a characteristic of lantibiotics. T he N-terminal amino acid sequence analysis indicated the first seven N-term inal amino acid residues as, NH2-K-K-K-S-G-V-I. The primary sequence showed significant homology to the lantibiotics lacticin 481 from Lactococcus lac tis and variacin from Micrococcus varians, which suggests that bacteriocin ISK-1 is a novel lantibiotic belonging to a lacticin-481 type.