Expression of beta subunit modulates surface potential sensing by calcium channels.
We have expressed the alpha 1 A calcium channel subunit alone, and in combination with different beta subunits, and investigated the effect of the external Ba2+ concentration on the voltage dependence of activation. Increasing the external Ba2+ concentration from 2.5 to 40 mM induced in all cases a depolarising shift of the potential for half-activation. The magnitude of this shift however, was different depending on whether the alpha 1 A subunit was expressed alone or with a beta subunit. Consistently, calculated external surface-charge density and potential were larger when a beta subunit was expressed. These results suggest that expression of an auxiliary subunit can influence calcium channel gating by modifying the sensitivity of the voltage sensor to the membrane potential profile.
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CRBM CNRS UPR 1086, 1919, Route de Mende, 34293 Montpellier, France.
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D000818:Animals; D001464:Barium / Q000494:pharmacology; D015220:Calcium Channels / Q000235:genetics / Q000502:physiology*; D004553:Electric Conductivity; D004563:Electrochemistry; D005260:Female; D015870:Gene Expression; D018014:Gene Transfer Techniques; D008564:Membrane Potentials; D009865:Oocytes / Q000378:metabolism; D011994:Recombinant Proteins; D014981:Xenopus
D015220:Calcium Channels; D011994:Recombinant Proteins; D001464:Barium