Immunological and binding studies on chloroform--methanol extracts from electroplax of Torpedo marmorata and from rat brain cortex. Comparison of the material solubilized by organic solvents with the receptor proteins solubilized by detergents
We have investigated a chloroform--methanol extracted material from electric organ of Torpedo marmorata with respect to binding of [3H]-acetyl-alpha-neurotoxin and [3H]-acetylcholine. No binding was observed which is in contrast to observations with detergent extracted receptor. Further, no crossreactivity could be demonstrated between the chloroform--methanol extracted proteolipid and antibodies against the detergent extracted receptor. Labelling in the membrane with [3H]-acetyl-alpha-neurotoxin before extraction with chloroform--methanol gave a very low yield of extracted labelled compound. The protein yield is about 0.3% of the total in the homogenate and only 0.04% of the specifically bound neurotoxin. Using the alkylating affinity label [3H]-N-propylbenzilylcholine mustard (1) and also [3H]-atropine, which both bind, at low concentrations, specifically to the muscarinic acetylcholine receptor, binding was studied to the chloroform--methanol extracted proteolipid from rat brain cortex. No specific binding could, however, be demonstrated. Prelabelling in the membrane with 1 and subsequent extraction with chloroform--methanol gave a protein yield of about 1% and an extraction of 26% of the specifically bound label.