Spatial Structure and Activity Mechanism of a Novel Spider Antimicrobial Peptide^,

Abstract

Latarcins (Ltc), linear peptides (ca. 25 amino acid long) isolated from the venom of the Lachesana tarabaevi spider, exhibit a broad-spectrum antibacterial activity, most likely acting on the bacterial plasmatic membrane. We study the structure-activity relationships in the series of these compounds. At the first stage, we investigated the spatial structure of one of the peptides, Ltc2a, and its mode of membrane perturbation. This was done by a combination of experimental and theoretical methods. The approach includes (i) structural study of the peptide by CD spectroscopy in phospholipid liposomes and by (1)H NMR in detergent micelles, (ii) determination of the effect on the liposomes by a dye leakage fluorescent assay and (31)P NMR spectroscopy, (iii) refinement of the NMR-derived spatial structure via Monte Carlo simulations in an implicit water-octanol slab, and (iv) calculation of the molecular hydrophobicity potential. The molecule of Ltc2a was found to consist of two helical regions (residues 3-9 and 13-21) connected via a poorly ordered fragment. The effect of the peptide on the liposomes suggests the carpet mechanism of the membrane deterioration. This is also supported by the analysis of hydrophobic/hydrophilic characteristics of Ltc2a and homologous antimicrobial peptides. These peptides exhibiting a helix-hinge-helix structural motif are characterized by a distinct and feebly marked amphiphilicity of their N- and C-terminal helices, respectively, and by a hydrophobicity gradient along the peptide chain. The approach we suggested may be useful in studying not only other latarcins but also a wider class of membrane-active peptides.

Antibacterial activity of venom from funnel web spider Agelena labyrinthica (Araneae: Agelenidae)

“…These peptides are supposed to increase membrane permeability by formation of either distinct channels or pores and to lyse both prokaryotic and eukaryotic cells (4,7,21). To observe morphological alterations after cell incubation in crude venom, scanning electron microscopy (SEM) was employed.…”

Latarcins: versatile spider venom peptides

“…At the same time, several Ltc (1 and 7) do not disrupt planar membranes, but cause some conductance changes. This was attributed to specific peculiarities in the hydrophobic/hydrophilic properties of the helices formed by Ltc in lipid membranes [31,32,69].…”

“…Peptides featuring a high proportion of either negatively [80] or positively charged amino acid residues in their sequences [31,32] are usually highly water-soluble and disordered in aqueous solution. According to CD spectroscopy [28] and 1 H-NMR data [31,32], this is the case for Ltc 1, 2a, 4a/4b, 5, 6a, and 7.…”

“…They display membrane activity and cytotoxic effects against bacteria [28] and mammalian cells [29,30]. Studies of their interaction with model lipid membranes [31][32][33][34] or with whole cells [29,30] are a well-established methodology for characterization of membrane-active properties in LP. Similarly the venom of Cupiennius salei features the presence of numerous cupiennins [35], and Oxyopes takobius produces a number of oxyopinins [36,37] (Table 1).…”

Infectious disease: Connecting innate immunity to biocidal polymers

“…Monte Carlo (MC) simulations of latarcins, a linear peptide, in a water-octanol slab revealed a peripheral mode of its membrane binding. The results of modeling and experimental techniques suggested the peptide acts by the carpet mechanism [209]. Ding and coworkers investigated the detailed structural information of different peptides interacting with lipid molecules [211].…”