Zorov D B, Kinnally K W, Tedeschi H
Department of Bioenergetics, A. N. Belozersky Laboratory of Molecular Biology, Moscow State University, USSR.
J Bioenerg Biomembr. 1992 Feb;24(1):119-24. doi: 10.1007/BF00769538.
The patch clamp records obtained from mitoplast membranes prepared in the presence of a calcium chelator generally lack channel activity. However, multiconductance channel (MCC) activity can be induced by membrane potentials above +/- 60 mV [Kinnally et al., Biochem. Biophys. Res. Commun. 176, 1183-1188 (1991)]. Once activated, the MCC activity persists at all voltages. The present report characterizes the activation by voltage of multiconductance channels of rat heart inner mitochondrial membranes using patch-clamping. In some membrane patches, the size of single current transitions progressively increases with time upon application of voltage. The inhibitor cyclosporin has also been found to decrease channel conductance in steps. The results suggest that voltage-induced effects which are inhibited by cyclosporin A are likely to involve either an increase in effective pore diameter or the assembly of low-conductance units. In activated patches, we have found at high membrane potentials (e.g., 130 mV) changes in conductance as high as 5 nS occurring in large steps (up to 2.7 nS). These were generally preceded by a smaller transition. Similar results were obtained less frequently at lower voltages. These results can be explained on the assumption that once assembled the channels may act in unison.
在存在钙螯合剂的情况下制备的线粒体膜的膜片钳记录通常缺乏通道活性。然而，多电导通道（MCC）活性可由高于+/- 60 mV的膜电位诱导[金纳利等人，《生物化学与生物物理研究通讯》176，1183 - 1188（1991）]。一旦被激活，MCC活性在所有电压下都持续存在。本报告使用膜片钳技术对大鼠心脏线粒体内膜多电导通道的电压激活进行了表征。在一些膜片中，施加电压后单个电流跃迁的大小会随时间逐渐增加。还发现抑制剂环孢菌素会逐步降低通道电导。结果表明，被环孢菌素A抑制的电压诱导效应可能涉及有效孔径的增加或低电导单元的组装。在激活的膜片中，我们发现在高膜电位（例如130 mV）下，电导变化高达5 nS，以大的步长（高达2.7 nS）发生。这些变化通常之前会有一个较小的跃迁。在较低电压下较少获得类似结果。这些结果可以基于这样的假设来解释，即通道一旦组装可能会协同作用。
