Plantaricin W from Lactobacillus plantarum belongs to a new family of two-peptide lantibiotics

Plantaricin W (Plw) is a new two-peptide bacteriocin, from Lactobacillus pl antarum, which inhibits a large number of Gram-positive bacteria. The two p eptides, Plw alpha (comprising 29 residues) and Plw beta (comprising 32 res idues), were isolated from the culture supernatants and characterized. The individual peptides had low antimicrobial activity but acted synergisticall y, and synergism was seen at all mixing ratios tested. The data indicate th at the two peptides work in a 1:1 ratio. Chemical analyses showed that both peptides are lantibiotics, but two unmodified cysteines and one serine res idue were present in Plw alpha, and Plw beta contained one cysteine residue . The Plw structural genes were sequenced and shown to encode prepeptides w ith sequence similarities to two other two-peptide lantibiotics, namely sta phylococcin C55 and lacticin 3147, The conserved residues are mainly serine s, threonines and cysteines that can be involved in intramolecular thioethe r bond formation in the C-terminal parts of the molecules. This indicates t hat these bacteriocins are members of a new family of lantibiotics with com mon bridging patterns, and that the ring structures play an important funct ional role. Based on the data a structural model is presented in which each peptide has a central lanthionine and two overlapping thioether bridges cl ose to their C-termini.