Tanaka J C
Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia 19104-6089.
Biophys J. 1993 Dec;65(6):2517-23. doi: 10.1016/S0006-3495(93)81294-3.
Macroscopic 3',5'-guanine cyclic monophosphate (cGMP)-activated currents from photoreceptor outer segment membranes were examined as the pH on the cytoplasmic face of inside/out patches was reduced. In the absence of divalent cations, protons reduced the current in both directions without affecting the shape of the current-voltage relation consistent with a voltage-independent block. When Ca2+ was added to the bath, increasing the [H+] relieved the Ca2+ block and eliminated the Ca(2+)-induced reversal potential shifts seen at pH 7.4. These results suggest that protons alter Na+/Ca2+ permeability of the channel and relieve Ca2+ block of the sodium transport.
当从内向外膜片的胞质面的pH降低时，检测了来自光感受器外段膜的宏观3',5'-环磷酸鸟苷（cGMP）激活电流。在没有二价阳离子的情况下，质子在两个方向上都降低了电流，而不影响电流-电压关系的形状，这与电压无关的阻断一致。当向浴槽中加入Ca2+时，增加[H+]可缓解Ca2+阻断，并消除在pH 7.4时观察到的Ca(2+)诱导的反转电位偏移。这些结果表明，质子改变了通道的Na+/Ca2+通透性，并缓解了钠转运的Ca2+阻断。
