STRUCTURE, SYNTHESIS, AND MOLECULAR-CLONING OF DERMASEPTIN-B, A FAMILY OF SKIN PEPTIDE ANTIBIOTICS

Analysis of antimicrobial activities that are present in the skin secr etions of the South American frog Phyllomedusa bicolor revealed six po lycationic (lysine-rich) and amphipathic alpha-helical peptides, 24-33 residues long, termed dermaseptins B1 to B6, respectively, Prepro-der maseptins B all contain an almost identical signal peptide, which is f ollowed by a conserved acidic propiece, a processing signal Lys-Arg, a nd a dermaseptin progenitor sequence. The 22-residue signal peptide pl us the first 3 residues of the acidic propiece are encoded by conserve d nucleotides encompassed by the first coding exon of the dermaseptin genes. The 25-residue amino-terminal region of prepro-dermaseptins B s hares 50% identity with the corresponding region of precursors for D-a mino acid containing opioid peptides or for antimicrobial peptides ori ginating from the skin of distantly related frog species. The remarkab le similarity found between prepro-proteins that encode end products w ith strikingly different sequences, conformations, biological activiti es and modes of action suggests that the corresponding genes have evol ved through dissemination of a conserved ''secretory cassette'' exon.