Neely A, Olcese R, Wei X, Birnbaumer L, Stefani E
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030.
Biophys J. 1994 Jun;66(6):1895-903. doi: 10.1016/S0006-3495(94)80983-X.
The alpha 1 subunit of cardiac Ca2+ channel, expressed alone or coexpressed with the corresponding beta subunit in Xenopus laevis oocytes, elicits rapidly inactivating Ca2+ currents. The inactivation has the following properties: 1) It is practically absent in external Ba2+; 2) it increases with Ca2+ current amplitudes; 3) it is faster at more negative potentials for comparable Ca2+ current amplitudes; 4) it is independent of channel density; and 5) it does not require the beta subunit. These findings indicate that the Ca2+ binding site responsible for inactivation is encoded in the alpha 1 subunit and suggest that it is located near the inner channel mouth but outside the membrane electric field.
心脏钙通道的α1亚基，单独表达或与相应的β亚基在非洲爪蟾卵母细胞中共表达时，会引发快速失活的钙电流。这种失活具有以下特性：1）在外部钡离子存在时几乎不存在；2）随钙电流幅度增加；3）在可比的钙电流幅度下，在更负的电位时失活更快；4）与通道密度无关；5）不需要β亚基。这些发现表明，负责失活的钙结合位点由α1亚基编码，并表明其位于通道内口附近但在膜电场之外。
