[Solubilization by various detergents, of the muscarinic cholinoreceptor and its complex with quinuclidinyl...

The possibilities to solubilize the rat brain cortex muscarinic acetylcholine receptor and its complex with [3H]-L-quinuclidinyl benzilate (QNB) were studied, using 14 detergents. It was shown that the native muscarinic cholinoreceptor was solubilized in addition to digitonin, also by CHAPS, with a 6% yield. Besides, the receptor-QNB complex was solubilized with the detergents Triton X-100, -102, -114, -165 (with 30% and 50% yields) and within a narrow concentration range with sodium dodecyl sulfate (50% yield). Some detergents of the Tween series, e.g., Triton X-45 and -305, as well as sodium deoxycholate and sodium oxycholate, did not solubilize the native receptor and its complex with QNB. It was found that yield of receptor solubilization did not exceed half of the total number of the receptor sites in the membranes, despite the fact that different concentrations of detergents were applied. The solubilization yield did not increase, when different mixtures of detergents were used. It was assumed that incomplete solubilization of the receptor protein reflects its heterogeneity in the membrane structure.