Effect of N-terminal Truncation of the Latarcin Ltc2a on Its Cytotoxic Properties and Interaction with Membranes

Vorontsova O.V., Egorova N.S.1, Arseniev A.S.1, Feofanov A.V.1

Department of Bioengineering, Biological Faculty, Moscow State University, ul. Vorobyevy Gory 1, bld.12, Moscow, 119992, Russia, +7(495)9395738,

1Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry RAS, ul. Miklukho-Maklaya 16/10, Moscow, 117997, Russia, +7(495)3366455

Ltc2a isolated from the venom of the spider Lachesana tarabaevi is a linear cationic peptide that exhibits bactericidal activity at micromolar and sub-micromolar concentrations in vitro [1]. Plasma membrane damage is the most probable mechanism of its antibacterial action. We have studied the influence of the N-terminal cluster of hydrophobic aminoacid residues on biological activity of Ltc2a. The deletion of four N-terminal residues one by one resulted in a gradual decrease in haemolytic activity and bactericidal effect against Staphylococcus aureus, whereas activity against Gram-negative bacteria was affected weakly.

In order to clarify structure-function relationships we have performed conformational analysis of the peptides bound at zwitterionic and anionic membranes using circular dichroism spectroscopy. All the peptides exhibit high propensity to alfa-helix formation in 50% trifluoroethanol. Binding of Ltc2a and its derivatives at zwitterionic membranes is accompanied with a conformational transition from a random coil to an alfa-helical structure. The truncation leads to a decrease in binding affinity at zwitterionic membranes that correlates strongly with a decrease in haemolytic activity. Ltc2a forms a beta-sheet structure at anionic membranes. The truncation of N-terminal residues results in gradual conformational changes from beta-sheet to alfa-helix.

In the report we discuss how the shortening of the hydrophobic motif of Ltc2a modulates its biological activity via the balance of electrostatic and hydrophobic interactions with lipid membranes. Fine correction of haemolytic vs. antibacterial activity seems to be a useful way to design antimicrobial peptides with increased therapeutic potential.

This work was supported by the Russian Foundation for Basic Researches (grant no. 07-04-01166) and in part by the Russian Federation Federal Agency for Science and Innovations (contract No. 02.467.11.3003).