Prolixicin: a novel antimicrobial peptide isolated from Rhodnius prolixus with differential activity against bacteria and Trypanosoma cruzi.

We identified and characterized the activity of prolixicin, a novel antimicrobial peptide (AMP) isolated from the hemipteran insect, Rhodnius prolixus. Sequence analysis reveals one region of prolixicin that may be related to the diptericin/attacin family of AMPs. Prolixicin is an 11-kDa peptide containing a putative 21 amino acid signal peptide, two putative phosphorylation sites and no glycosylation sites. It is produced by both adult fat body and midgut tissues in response to bacterial infection of the haemolymph or the midgut. Unlike most insect antibacterial peptides, the prolixicin gene does not seem to be regulated by NF-κB binding sites, but its promoter region contains several GATA sites. Recombinant prolixicin has strong activity against the Gram-negative bacterium Escherichia coli and differential activity against several Gram-negative and Gram-positive bacteria. No significant toxicity was demonstrated against Trypanosoma cruzi, the human parasite transmitted by R. prolixus.