Primary and secondary structures of grammistins, peptide toxins isolated from the skin secretion of the soapfish Pogonoperca punctata

Six peptides (grammistins Pp 1, 2a, 2b, 3, 4a and 4b) with both hemolytic a nd ichthyotoxic activities were isolated from the skin secretion of the soa pfish Pogonoperca punctata by gel filtration and reverse-phase high perform ance liquid chromatography. They were completely sequenced and found to be simple peptides differing from the previous suggestion that they are peculi ar peptides with tertiary amine or quaternary ammonium base moieties. Gramm istins Pp 1, 2a and 2b were composed of 13 residues, Pp 3 of 25 residues an d Pp 4a and 4b of 24 residues. While grammistins Pp 4a and 4b were identica l and highly homologous with grammistin Gs 2 previously isolated from anoth er soapfish Grammistes sexlineatus, the other grammistins did not have homo logies with any proteinic or peptidic toxins known to date. Judging from ci rcular dichroism data, helical wheel projections and hydrophobic moment plo ts, all the isolated grammistins are surface-seeking peptides with an abund ance in amphiphilic alpha -helicity, similar to pardaxins from the skin sec retion of two species of soles and melittin from bee venom as well as the G . sexlineatus grammistins.