Dermaseptin-S8 peptide

Dermaseptin sVIII has only one site of amino acid substitution when compared with dermaseptin sI. Unlike dermaseptin s1, mature dermaseptin sVI–sVIII peptides lacked the C-terminal tripeptide (-GE/AQ) of the precursor openreading frame deduced from their respective cDNAs. MS/ MS fragmentation of each peptide using a QTOF-Ultima instrument (Micromass, UK), established that each was C terminally amidated with either an isoleucine amide (sVI) or a glutamine amide (sVII–sVIII). The defensive skin secretions of frogs are known to contain a plethora of biologically active peptides, some of which share common primary structural features with endogenous vertebrate regulatory peptides and others that appear to have no obvious structural counterparts in higher vertebrates. The dermaseptins constitute a group of peptides that fall into the latter category displaying broad spectrum antimicrobial activity against both bacteria and fungi The role of this peptide family, typically consisting of 27–34 amino acid residues, is thought to be in defending the naked moist skin of the frogs against environmental or pathogenic microbial invasion. One must bear in mind that the integument of the amphibian plays many important physiological roles including respiration and osmoregulation—fundamental processes that could impinge upon the well-being of the animal if impaired by microbial colonisation. In fact, dermaseptins were the first vertebrate peptides to exhibit lethal effects against the filamentous fungi responsible for severe opportunistic infections accompanying immunodeficiency syndrome and the use of immunosuppressive agents.