Calcium channel beta-subunit binds to a conserved motif in the I-II cytoplasmic linker of the alpha 1-subunit.
The beta-subunit is an integral component of purified voltage-sensitive Ca2+ channels. Modulation of Ca2+ channel activity by the beta-subunit, which includes significant increases in transmembrane current and/or changes in kinetics, is observed on coexpression of six alpha 1-subunit genes with four beta-subunit genes in all alpha 1-beta combinations tested. Recent reports suggest that this regulation is not due to targeting of the alpha 1-subunit to the plasma membrane but is probably a result of a conformational change induced by the beta-subunit. Here we report that the beta-subunit binds to the cytoplasmic linker between repeats I and II of the dihydropyridine-sensitive alpha 1-subunits from skeletal (alpha 1S) and cardiac muscles (alpha 1C-a), and also with the more distantly related neuronal alpha 1A and omega-conotoxin GVIA-sensitive alpha 1B-subunits. Sequence analysis of the beta-subunit binding site identifies a conserved motif (QQ-E--L-GY--WI--E) positioned 24 amino acids from the IS6 transmembrane domain in each alpha 1-subunit. Mutations within this motif reduce the stimulation of peak currents by the beta-subunit and alter inactivation kinetics and voltage-dependence of activation. Conservation of the beta-subunit binding motif in these functionally distinct calcium channels suggests a critical role for the I-II cytoplasmic linker of the alpha 1-subunit in channel modulation by the beta-subunit.
Pragnell
M
M
Howard Hughes Medical Institute, Department of Physiology, University of Iowa College of Medicine, Iowa City 52242.
De Waard
M
M
Mori
Y
Y
Tanabe
T
T
Snutch
T P
TP
Campbell
K P
KP
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015220:Calcium Channels / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D020746:Calcium Channels, L-Type; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D004095:Dihydropyridines / Q000494:pharmacology; D000939:Epitopes; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017421:Sequence Analysis; D020866:omega-Conotoxin GVIA
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D004095:Dihydropyridines; D000939:Epitopes; D009124:Muscle Proteins; D010455:Peptides; D011993:Recombinant Fusion Proteins; C038806:1,4-dihydropyridine; D020866:omega-Conotoxin GVIA