Dihydropyridine binding of the calcium channel complex from skeletal muscle is modulated by subunit interaction.
The dihydropyridine-binding subunit alpha 1 of the calcium channel complex from rabbit skeletal muscle can be partially depleted from the alpha 2 delta beta-complex using wheat germ agglutinin-affinity chromatography. This depletion of the alpha 1 from the other subunits leads to a loss of dihydropyridine-binding, which can be fully reconstituted by repletion of the alpha 1 with the other subunits. Reassembly of these subunits results in an increase in the Kd and Bmax of the dihydropyridine-binding indicating that the non-dihydropyridine-binding subunits influence dihydropyridine-binding. The affinity of the alpha 1 subunit for the other subunits was determined to be approximately 35 nM. Since the free alpha 1 subunit will not bind to the beta subunit alone, there is evidence, given the selective partitioning of the beta subunit to the lectin-bound subunit pool, that either beta binds with higher affinity to the alpha 2 delta-complex than to the free alpha 1 subunit or that the bound alpha 1 creates or modulates beta-binding. This indicates a functional high affinity interaction between the dihydropyridine-binding alpha 1 subunit and the alpha 2 delta beta-complex.
Woscholski
R
R
University of Freiburg, Institute of Molecular Cell Biology, Germany.
Marmé
D
D
D000818:Animals; D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D002846:Chromatography, Affinity; D004072:Digitonin / Q000494:pharmacology; D004095:Dihydropyridines / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000378:metabolism; D009124:Muscle Proteins / Q000302:isolation & purification / Q000378:metabolism* / Q000502:physiology; D011485:Protein Binding; D011487:Protein Conformation; D011817:Rabbits; D011978:Receptors, Nicotinic / Q000302:isolation & purification / Q000378:metabolism* / Q000502:physiology
D015220:Calcium Channels; D004095:Dihydropyridines; D006023:Glycoproteins; D009124:Muscle Proteins; D011978:Receptors, Nicotinic; C038806:1,4-dihydropyridine; D004072:Digitonin