Generation and characterization of the antibacterial activity of a novel hybrid antimicrobial peptide comprising functional domains from different insect cecropins

Abstract

The search for new antimicrobial compounds involves finding novel sources of chemotherapeutic compounds or manipulating and combining structures from existing molecules. Small antimicrobial peptides (AMPs) are components of innate immune defenses characterized in greatest detail in insect-derived AMPs. We have generated hybrid AMPs (hAMPs) by combining functional motifs from different insect AMPs as a proof of principle that we can generate molecules with lower minimum inhibitory concentrations, and with different activity and target specificity than either parent molecule. A two-helix, cecropin-like hAMP was created by linking the N-terminal alpha helix of cecropin A from Aedes aegypti to the C-terminal alpha helix of cecropin A1 from Drosophila melanogaster. This molecule exhibits antibacterial activity at sub-micromolar concentrations with a target specificity that differs from either parent molecule. Antibacterial activity of the hybrid molecule was found to be greater against Gram-negative than Gram-positive bacteria. No hemolysis was observed in sheep red blood cells exposed to concentrations up to 50 micromol/L, suggesting the peptide is not detrimental to eukaryotic cells.

Venom of Parasitoid Pteromalus puparum Impairs Host Humoral Antimicrobial Activity by Decreasing Host Cecropin and Lysozyme Gene Expression

“…The antimicrobial activities of cecropins are related to their binding capability. These activities are usually composed of a strongly basic N -terminal region for binding to the microbial membranes and a long hydrophobic C -terminal stretch to form two short α-helices that facilitate the membrane-invasive activity [ 61 ]. Additionally, lysozyme is another important molecule in the innate immune system, including insect immunity.…”

Induction of a Peptide with Activity against a Broad Spectrum of Pathogens in the Aedes aegypti Salivary Gland, following Infection with Dengue Virus

“…For example, the C-terminal amidation of these peptides might enhance their stability and cationicity, as has been demonstrated for the C-terminally amidated cecropin A of the giant silk moth Hyalophora cecropia which is more active than cecropin A itself [47]. Otherwise, as the antimicrobial activity of several of these analogs is more potent than that of their parent molecules [48], hybrid molecules based on the structure of MK and GK peptides could be powerful effectors. Insect AMPs have been selected throughout evolution for their low toxicity to eukaryotic cells.…”

Cotesia plutellae bracovirus suppresses expression of an antimicrobial peptide, cecropin, in the diamondback Moth, Plutella xylostella, challenged by bacteria

“…This antimicrobial activity is predicted by the structural characters of cecropins. They are composed of a strongly basic Nterminal region for binding to the bacterial membranes and a long hydrophobic C-terminal stretch to form two shorthelices that facilitate the membrane-invasive activity (Plunkett et al, 2009).…”