Solution structures and model membrane interactions of Ctriporin, an anti-methicillin-resistant Staphylococcus aureus Peptide from Scorpion Venom.

Ctriporin peptide (Ctr), a novel antimicrobial peptide isolated from the venom of the scorpion Chaerilus tricostatus, shows a broad-spectrum of antimicrobial activity and is able to inhibit antibiotic resistant pathogens, including Methicillin resistant Staphylococcus aureus, Methicillin Resistant Coagulase-negative Staphylococcus, and Penicillin Resistant Staphylococcus epidermidis strains. To understand the active conformation of the Ctr peptide in membranes, we have investigated the interaction of Ctr with the negatively charged and zwitterionic membrane-mimetic micelles such as sodium dodecyl sulphate (SDS) and n-dodecylphosphocholine (DPC), respectively. The interactions were studied using fluorescence and circular dichroism (CD) spectroscopy. Fluorescence experiments revealed that the N-terminus tryptophan residue of Ctr interacted with the hydrophobic core of the membrane mimicking micelles. The CD results suggest that interactions with membrane-mimetic micelles induce an α-helix conformation in Ctr. Moreover, we have determined the solution structures of Ctr in SDS and DPC micelles using nuclear magnetic resonance (NMR) spectroscopy. The structural comparison of Ctr in the presence of SDS and DPC micelles showed significant conformational changes. The observed structural differences of Ctr in anionic versus zwitterionic membrane-mimetic micelles suggest that the mode of interaction of this peptide may be different in two environments which may account for its ability to differentiate bacterial and eukaryotic cell membrane.