Chemical synthesis, molecular modeling, and antimicrobial activity of a novel bacteriocin, MMFII

A new antimicrobial peptide, referred to as MMFII, was purified to homogene ity from lactic acid bacteria Lactococcus lactis, which were isolated from Tunisian dairy product. The complete amino acid sequence of the peptide has been established by amino acid analysis, Edman sequencing, and mass spectr ometry and verified by solid-phase chemical synthesis. MMFII is a single-ch ain 37-residue polypeptide containing a single intramolecular disulfide bon d, i.e., TSYGNGVHCNKSKCWIDVSELETYKAGTVSNPKDILW. It shares ca. 35% sequence identity with Leucocin A, a class IIa bacteriocin. Modeling based on the 3- D of Leucocin A shows three beta strands located in the N-terminal region ( Thr1-Tyr3, Val7-Asn10, Lys13-Ile16) and an alpha helical domain from Asp17 to Asn31. When plotted as an alpha -helical wheel, the central alpha -helix of MMFII does not exhibit an amphipathic helical structure. The synthetic MMFII (sMMFII), obtained by the solid-phase method, was shown to be indisti nguishable from the natural peptide. sMAFII is active against Lactococcus c remoris and Listeria ivanovii bacteria, whereas no activity was detected fo r any of the synthetic N-terminal truncated MMFII analogs Cys9-Trp37, Trp15 -Trp37, and Val18-Trp37. (C) 2001 Academic Press.