Interactions between ƒÑ-Conotoxin MI and the Torpedo marmorata receptor ƒÑ-ƒÔ interface

LEONARDO CORTÉZ; CRISTINA MARINO BUSLJE; MIRTHA BISCAGLIO DE JIMENEZ BONINO; ULF HELLMAN

BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS

ELSEVIER

Año: 2007 vol. 30 p. 275 - 279

0006-291X

AbstractThe muscle-type nicotinic receptor has two distinguishable acetylcholine binding sites at the a–c and a–d subunit interfaces; a-conotoxinscan bind them selectively. Moreover, we previously reported that a-conotoxin MI can interact with Torpedo californica and Torpedomarmorata receptors showing that conotoxins can also detect receptors from different species of the same genus [L. Cortez, S.G. delCanto, F. Testai, M.B. de Jime´nez Bonino, Conotoxin MI inhibits the acetylcholine binding site of the Torpedo marmorata receptor,Biochem. Biophys. Res. Commun. 295 (2002) 791–795]. Herein, to identify T. marmorata receptor regions involved in a-conotoxinMI binding, a photoactivatable reagent was used and labeled sites were mapped by enzymatic proteolysis, MALDI-TOF-MS and Edmandegradation. a-Conotoxin MI binding determinants were found and studies revealed a second binding motif at the a/d interface. A proposalfor receptor–toxin interaction is discussed based on experimental results and docking studies. 2007 Elsevier Inc. All rights reserved.Keywords: Nicotinic receptors; Torpedo marmorata; a-Conotoxin MI; Ligand-binding sites; Conus