IDENTIFICATION OF A 2ND MEMBRANE-ACTIVE 13-RESIDUE PEPTIDE SEGMENT INTHE ANTIMICROBIAL PROTEIN, BOVINE SEMINALPLASMIN

Seminalplasmin (SPLN) is a 47-residue protein from bovine seminalplasm a having broad-spectrum antibacterial activity. The protein has no hem olytic activity. SPLN interacts with lipid vesicles and its antibacter ial activity appears to stem from its ability to permeabilize the bact erial plasma membrane. Analysis of SPLN's primary structure, with resp ect to its relative hydrophobicity and hydrophilicity, revealed a segm ent, PKLLETFLSKWIG, more hydrophobic than the rest of the protein. A s ynthetic peptide corresponding to this region bad not only antibacteri al activity but also hemolytic properties. Analysis of the SPLN sequen ce based on hydrophobic moment plots has revealed a second segment, SL SRYAKLANRLA, which could be membrane active. A synthetic peptide corre sponding to this region shows only antibacterial activity with no hemo lytic activity.