Rotational molecular dynamics of the membrane-bound acetylcholine receptor revealed by phosphorescence spectroscopy

BARTHOLDI M; BARRANTES FJ; JOVIN TM

EUROPEAN JOURNAL OF BIOCHEMISTRY

John Wiley and Sons

Lugar: Washington DC; Año: 1981 vol. 120 p. 389 - 397

0014-2956

The rotational mobility of the membrane-bound acetylcholine receptor from Torpedo marmorata has been studied by phosphorescence anisotropy techniques using eosin-5?-isothiocyanate and eosin-5?-iodoacetamide derivatives of the a-neurotoxin of Bungarus multicinctus (a-bungarotoxin). Normal membranes, those depleted of nonreceptor peripheral peptides by alkaline treatment, as well as membranes subjected to various chemical modifications of the thiol groups, have been characterized. Rotational correlation times (10 - 26 ps) compatible with the motion of individual 9-S monomeric receptor species of M, 250000 were observed upon reduction of the membranes with dithiothreitol or by raising the temperature to 39 ?C in the case of alkaline-treated membranes. Membranes prepared throughout in N-ethylmaleimide, which yield upon detergent solubilization a predominant 13-S diiiieric species and which are not depleted of the nonreceptor v-peptide (M, 43000) by alkaline treatment, are relatively more ?rigid? than normal membranes and do not show the anisotropy components characteristic of the monomeric receptor. The influence of the v-peptide on the structural stability of the receptor oligomeric forms and the thiol-dependent interconversions are thus reflected in the time-dependent spectroscopic measurements.