[Gly^1, Leu^2, Ala^3]mastoparan T enhanced the original catecholamine releasing activity from chromaffin cells

Abstract

Mastoparan T(MT), one of the mastoparan family, and five mastoparan T analogs designed by N-terminal three residues-replacement of MT to Gly-Leu-Ala(GLA-MT), a deletion of N-terminal three residues(MT-GG-11)and Gly residue(s)-replacement at the position 5 and / or 8(GLA-MT-AG, GLA-MT-GA and GLA-MT-GG)were synthesized in a liquid phase manual manner. Catecholamine releasing activity of these synthetic peptides for adrenal chromaffin cells were investigated. GLA-MT had about two times as much as the releasing activity of MT and was the most active molecule of all the mastoparan T analogs. GLA-MT-GG had almost no releasing activity, but increased twice catecholamine releasing activity of mastoparan after pretreatment of adrenal chromaffin cells by the peptide at a high concentration. The circular dichroism difference spectra of synthetic peptides in the presence of trifluo-roethanol or Ca^2+-calmodulin, and these biological activities such as the binding activity to calmodulin-Sepharose 4B and erythrocyte ghost, and hemolytic activity were also examined. Mastoparan stimulates guanine nucleotide exchange by guanosine 5'-triphosphates-binding proteins, which is an initial event of signal transduction to the cytoplasm. It was suggested that the potent active mastoparan analogs would be able to be synthesized as a useful tool for the elucidation of transduction mechanism or the related disorders.