Effects on electrophoretic mobility and antibacterial spectrum of removal of two residues from synthetic sarcotoxin IA and addition of the same residues to cecropin B

Cecropin B and cecropin IA (sarcotoxin IA) are 35- and 39-residue antibacterial peptides from a silk moth and a meat fly, respectively. Using solid phase synthesis we have made these peptides as well as two 37-residue analogs, one containing a deletion of leucine and lysine (residues 2a and 2b) as compared to cecropin IA, the other containing an insertion of leucine and lysine at the corresponding place in cecropin B. This addition and removal of a lysine residue did not cause the expected change in electrophoretic mobility. When tested for antibacterial spectra, the insertion analog was found to be as active as the parent compound while the deletion analog had lost most of its antibacterial capacity. In addition it was shown that the C-terminal amide contributes to the broad spectrum properties of the cecropins.