Effect of L- to D-Peptide Isomerisation on the Activity of Antimicrobial Peptide Anoplin

Abstract

Isolated from the venom sac of solitary spider wasp, Anoplius samariensis, Anoplin is the smallest linear α-helical antimicrobial peptide found naturally up to date. It has broad spectrum activity against both Gram-positive and Gram-negative bacteria, and little hemolytic activity toward human erythrocytes (1,2). Previous studies showed that substitution of all amino acids in the peptide with D-isomers can increase the bioavailability and reduce peptide degradation without affecting the antimicrobial properties since the net charge and the hydrophobicity are retained (3). In the present work, two stereoisomers of Anoplin were studied using UV resonance Raman spectroscopy, Langmuir Blodgett, atomic force microscopy, calcein leakage assay and antimicrobial assay. UV resonance Raman data indicate that the two forms of the peptide adopt similar conformations in aqueous buffer and in membrane mimicking solutions. Monolayer isotherms show that D-Anoplin has a lightly greater area per molecule than L-Anoplin. Finally, membrane rupturing ability of both stereoisomers was found to depend strongly on membrane composition.(1) Konno, K., Hisada, M., Fontana, R., Lorenzi, C.C.B., Naoki, H., Itagaki, Y., Miwa, A., Kawai, N., Nakata, Y., Yasuhara, T., Neto, J.R., de Azevedo Jr., W.F., Palma, M.S. and Nakajima, T. (2001) Biochim. Biophys. Acta 1550: 70-80.(2) Ifrah, D., Doisy, X., Ryge, R.S. and Hansen, P.R. (2005) J. Pept. Sci. 11: 113-121.(3) Wade, D., Boman, A., Wahlin, B., Drain, C.M., Andreu, D., Boman, H.G. and Merrifield, R.B. (1990) Proc. Nat. Acad. Sci. 87: 4761-4765.