Interactions of selected insect neuropeptides with synthetic lipids

Interactions of the insect neuropeptide proctolin (Arg-Tyr-Leu-Pro-Thr), its [beta-cyclohexyl-(4-O-methyl)2]-L-alanine analog, and the leucopyrokinin [2-8]-fragment (Thr-Ser-Phe-Thr-Pro-Arg-Leu-NH2), with synthetic phospholipids (DPPC, DMPE, DMPG) were studied using the microcalorimetric method. Most pronounced changes of the lipid thermotropic behavior were observed with DMPG/leucopyrokinin [2-8]-fragment mixtures. Proctolin itself was less active with all the lipids studied. The results obtained suggest that the studied peptides interact with the head group region of lipid bilayer.