Effect of succinylation on the membrane activity and conformation of a short cecropin A-melittin hybrid peptide.

A 15-residue hybrid peptide (KWKLFKKIGAVLKVL-amide) incorporating partial sequences of cecropin A and melittin causes the release of carboxyfluoresceine encapsulated in phosphatidylcholine liposomes. Succinylation of the amino groups in the N-terminus and lysine side chains inhibits the effect of this peptide on liposome permeability. Conformational analysis of the parent peptide and its succinyl derivative by CD and nmr indicates that both peptides form amphipathic alpha-helices in the presence of hexafluoro-2-propanol, but only the unmodified peptide acquires a relevant level of alpha-helical conformation in the presence of liposomes.