2fr9

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NMR structure of the alpha-conotoxin GI (SER12)-benzoylphenylalanine derivative

Overview

alpha-Conotoxins are small peptides from cone snail venoms that function, as nicotinic acetylcholine receptor (nAChR)-competitive antagonists, differentiating between nAChR subtypes. Current understanding about the, mechanism of these selective interactions is based largely on mutational, analyses, which identify amino acids in the toxin and nAChR that determine, the energetics of ligand binding. To identify regions of the nAChR, involved in alpha-conotoxin binding by use of photoactivated, cross-linking, two benzoylphenylalanine (Bpa) analogs of alpha-conotoxin, GI, GI(Bpa12) and GI(Bpa4), were synthesized by replacing the respective, residues with Bpa, and their (1)H-NMR structures were determined. Both, analogs preserved the GI conformation, but only GI(Bpa12) displaced, (125)I-labeled GI from the Torpedo californica nAChR. (125)I-labeled, GI(Bpa12) bound to two sites on the receptor (K(d) 13 and 1800 nM), and on, UV irradiation specifically photolabeled the alpha, gamma and delta, subunits. Photolabeling sites were mapped by selective proteolysis and, enzymatic deglycosylation, combined with SDS/PAGE, HPLC and Edman, degradation. In the alpha subunit, cobratoxin-inhibited incorporation was, limited to the 22-kDa fragment beginning at alphaSer173 and containing the, agonist-binding site segment C. In the gamma subunit, radioactivity was, localized to two distinct peptides containing agonist-binding site, segments F and D: nonglycosylated 24-kDa and glycosylated 13-kDa fragments, starting at gammaAla167 and gammaAla49, respectively. The labeling of, these fragments is discussed in terms of a model of GI(Bpa12) bound to the, extracellular domain of the Torpedo nAChR homology model derived from the, cryo-electron microscopy structure of Torpedo marmorata nAChR and X-ray, crystal structures of snail acetylcholine-binding protein complexes with, agonists and antagonists.

About this Structure

2FR9 is a Single protein structure of sequence from [1]. Full crystallographic information is available from OCA.

Reference

alpha-Conotoxin GI benzoylphenylalanine derivatives. (1)H-NMR structures and photoaffinity labeling of the Torpedo californica nicotinic acetylcholine receptor., Kasheverov IE, Chiara DC, Zhmak MN, Maslennikov IV, Pashkov VS, Arseniev AS, Utkin YN, Cohen JB, Tsetlin VI, FEBS J. 2006 Apr;273(7):1373-88. PMID:16689926

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