Structure-activity relationships of omega-Agatoxin IVA in lipid membranes

Abstract

To analyze structural features of omega-Aga IVA, a gating modifier toxin from spider venom, we here investigated the NMR solution structure of omega-Aga IVA within DPC micelles. Under those conditions, the Cys-rich central region of omega-Aga IVA still retains the inhibitor Cys knot motif with three short antiparallel beta-strands seen in water. However, N-15 HSQC spectra of omega-Aga IVA within micelles revealed that there are radical changes to the toxin's C-terminal tail and several loops upon binding to micelles. The C-terminal tail of omega-Aga IVA appears to assume a beta-turn like conformation within micelles, though it is disordered in water. Whole-cell patch clamp studies with several omega-Aga IVA analogs indicate that both the hydrophobic C-terminal tail and an Arg patch in the core region of omega-Aga IVA are critical for Cav2.1 blockade. These results suggest that the membrane environment stabilizes the structure of the toxin, enabling it to act in a manner similar to other gating modifier toxins, though its mode of interaction with the membrane and the channel is unique. (C) 2016 Elsevier Inc. All rights reserved.