The effects of lipids on the structure of the eukaryotic cytolysin equinatoxin II: A synchrotron radiation circular dichroism spectroscopic study

Miles, AJ; Drechsler, A; Kristan, K; Anderluh, G; Norton, RS; Wallace, BA; Separovic, F

Author(s): Miles, AJ; Drechsler, A; Kristan, K; Anderluh, G; Norton, RS; Wallace, BA; Separovic, F;
Details: Publication Year 2008-10,Volume 1778,Issue #10,Page 2091-2096
Journal Title: BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
Publication Type: Journal Article
Abstract: Synchrotron radiation circular dichroism (SRCD) spectroscopy studies of the eukaryotic pore-forming protein equinatoxin II (EqtII) were carried out in solution and in the presence of micelles or small unilamellar vesicles (SUV) of different lipid composition. The SRCD structural data was correlated with calcein leakage from SUV and with partitioning of EqtII to liposomes, and micelles, according to haemolysis assays. The structure of EqtII in water and dodecylphosphocholine micelles as determined by SRCD was similar to the values calculated from crystal and solution structures of the protein, and no changes were observed with the addition of sphingomyelin (SM). SM is required to trigger pore formation in biological and model membranes, butour results suggest that SM alone is not sufficient to trigger dissociation of the N-terminal helix and further structural rearrangements required to produce a pore. Significant changes in conformation of EqtII were detected with unsaturated phospholipid (DOPC) vesicles when SM was added, but not with saturated phospholipids (DMPC), which suggests that not only is membrane curvature important, but also the fluidity of the bilayer. The SRCD data indicated that the EqtII structure in the presence of DOPC:SM SUV represents the 'bound' state and the 'free' state is represented by spectra for DOPC or DOPC:Chol vesicles, which correlates with the high lytic activity for SUV of DOPC:SM. The SRCD results provide insight into the lipid requirements for structural rearrangements associated with EqtII toxicity and lysis. (C) 2008 Elsevier B.V. All rights reserved.
Publisher: ELSEVIER SCIENCE BV
Keywords: PORE-FORMING TOXIN; PROTEIN SECONDARY STRUCTURE; ANEMONE STICHODACTYLA-HELIANTHUS; N-TERMINAL REGION; SEA-ANEMONE; PHOSPHOLIPID-VESICLES; MODEL MEMBRANES; ACTINIA-EQUINA; INFRARED-SPECTROSCOPY; STICHOLYSIN-II
Publisher's Version: https://doi.org/10.1016/j.bbamem.2008.04.001
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Creation Date: 2008-10-01 12:00:00