The inducible antibacterial peptides of the hemipteran insect Palomena prasina: Identification of a unique family of proline-rich peptides and of a novel insect defensin

Bacterial challenge induced the appearance of a strong antibacterial activity in the cell-free hemolymph of adult Palomena prasina (Hemiptera), We isolated several peptides that were capable of causing this activity and determined their primary sequence by Edman degradation and mass spectrometry. Four of the five isolated peptides are closely related small, strongly cationic, proline-rich peptides. They are not posttranslationnally modified, We propose the name of metalnikowins for these novel peptides, We have chemically synthesized metalnikowin I and analyzed its activity spectrum, which is primarily directed against Gram negative bacteria, Metalnikowin appears to be bacteriostatic. The fifth of the induced peptides which we have isolated from Palomena is a 43-residue novel isoform of insect defensins.