Photoaffinity labeling of the purified skeletal muscle calcium antagonist receptor by a novel benzothiazepine, [3H]azidobutyryl diltiazem.
Previous photoaffinity-labeling studies with [3H]azidopine, (+) [3H]PN200-110, and [3H]LU 49888 have demonstrated that 1,4-dihydropyridines (nifedipine-like drugs) and phenylalkylamines (verapamil-like drugs) bind exclusively to the 165-kDa alpha 1 subunit of skeletal muscle calcium channels. However, it has not been conclusively determined whether benzothiazepines (diltiazem-like drugs), which represent the third group of calcium antagonists, also bind to the alpha 1 subunit. Here we report data obtained with a newly developed benzothiazepine photoaffinity probe, [3H]azidobutyryl diltiazem. This drug competes with diltiazem for the benzothiazepine-binding site and, in purified calcium channel preparations, specifically labels the 165-kDa polypeptide which does not change its electrophoretic mobility upon disulfide reduction. These data show that benzothiazepines, just like 1,4-dihydropyridines and phenylalkylamines, bind to the alpha 1 subunit of the skeletal muscle calcium channels.
Naito
K
K
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Ohio 45267-0575.
McKenna
E
E
Schwartz
A
A
Vaghy
P L
PL
D000345:Affinity Labels / Q000378:metabolism*; D000818:Animals; D001386:Azides / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000378:metabolism*; D015220:Calcium Channels; D002462:Cell Membrane / Q000378:metabolism; D004110:Diltiazem / Q000031:analogs & derivatives* / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D009132:Muscles / Q000378:metabolism*; D010449:Peptide Mapping; D011817:Rabbits; D011978:Receptors, Nicotinic / Q000302:isolation & purification / Q000378:metabolism*
D000345:Affinity Labels; D001386:Azides; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D046911:Macromolecular Substances; D011978:Receptors, Nicotinic; C062012:3-(4-azidobutyryloxy)diltiazem; D004110:Diltiazem