1. Isolation and structures of grammistins, peptide toxins from the skin secretion of the soapfish Grammistes sexlineatus
K Shiomi, T Igarashi, H Yokota, Y Nagashima, M Ishida Toxicon. 2000 Jan;38(1):91-103. doi: 10.1016/s0041-0101(99)00136-1.
Two peptide toxins (named grammistins Gs 1 and Gs 2) with hemolytic and ichthyotoxic activities were isolated from the skin secretion of the soapfish Grammistes sexlineatus. Grammistin Gs 2 showed 6-11 x higher hemolytic activity and 10x higher ichthyotoxicity than grammistin Gs 1. The complete amino acid sequences of Gs 1 comprising 25 residues and Gs 2 comprising 24 residues were determined. Although a search by the database failed to find any homologous toxins from other sources, the grammistins were similar in secondary structures as well as biological activities to the two classes of peptide toxins, melittin from the bee venom and pardaxins from the skin secretion of two species of soles. CD experiments and helical wheel projections showed that the grammistins were randomly coiled in distilled water but formed amphiphilic alpha-helices in the presence of SDS micelles. In addition, they were found to be surface seeking peptides by the Eisenberg plot and assumed to exist as aggregates of 3-4 molecules. Interestingly, grammistin Gs 2 is much more abundant in amphiphilic alpha-helices and much higher in biological activities than melittin and pardaxins as well as grammistin Cs 1.
3. Further isolation and characterization of grammistins from the skin secretion of the soapfish Grammistes sexlineatus
Nami Sugiyama, Mika Araki, Masami Ishida, Yuji Nagashima, Kazuo Shiomi Toxicon. 2005 Apr;45(5):595-601. doi: 10.1016/j.toxicon.2004.12.021.
Soapfishes contain peptide toxins (grammistins) in the skin secretion. Two grammistins (Gs 1 and Gs 2) and six grammistins (Pp 1, Pp 2a, Pp 2b, Pp 3, Pp 4a and Pp 4b) have already been isolated from Grammistes sexlineatus and Pogonoperca punctata, respectively. In this study, five grammistins (Gs A-E), together with grammistins Gs 1 and Gs 2, were further isolated from G. sexlineatus by gel filtration and reverse-phase HPLC. Sequence analyses revealed that grammistins Gs A (28 residues) and Gs C (26 residues) are analogous to grammistin Pp 3 and grammistin Gs B (12 residues) to grammistin Pp 1, while grammistins Gs D (13 residues) and Gs E (13 residues) are identical with grammistins Pp 1 and Pp 2b, respectively. Grammistins Gs A-C exhibited antibacterial activity with a broad spectrum against nine species of bacteria in common with the other grammistins but had no hemolytic activity differing from the other grammistins. Grammistins Gs A-E, Gs 1 and Gs 2 could release carboxyfluorescein entrapped within liposomes made of either phosphatidylcholine or phosphatidylglycerol/phosphatidylcholine (3:1), demonstrating their membrane-lytic activity. However, no clear relationship between the membrane-lytic activity and the biological activity of grammistins was recognized.
