Liu S, Dubinsky W P, Haddox M K, Schultz S G
Department of Physiology and Cell Biology, University of Texas Medical School, Houston 77225.
Am J Physiol. 1991 Oct;261(4 Pt 1):C713-7. doi: 10.1152/ajpcell.1991.261.4.C713.
Using calmodulin-affinity chromatography, we have isolated a fraction of proteins from solubilized basolateral membranes of rabbit colonocytes which when reconstituted into planar phospholipid bilayers disclosed Ca(2+)-activated single K+ channel activities. The properties of the reconstituted channels are identical to those of native membrane vesicles incorporated into these bilayers with respect to their high selectivity for K+ over C-, high ("maxi") conductance, voltage gating, and inhibition by trifluoperazine. Two-dimensional sodium dodecyl sulfate gel electrophoresis of these proteins revealed three major protein species with molecular masses of 120, 60, and 35 kDa, which constituted 70, 10, and 20%, respectively, of the total protein. The results of other studies strongly suggest that the 35-kDa protein may be the Ca(2+)-activated K+ channel protein in these membranes.
利用钙调蛋白亲和层析法，我们从兔结肠细胞基底外侧膜的可溶部分中分离出了一部分蛋白质。当将这些蛋白质重组到平面磷脂双分子层中时，发现了钙激活的单钾离子通道活性。重组通道的特性与掺入这些双分子层的天然膜囊泡的特性相同，即对钾离子的选择性高于氯离子、高（“大”）电导、电压门控以及受三氟拉嗪抑制。这些蛋白质的二维十二烷基硫酸钠凝胶电泳显示出三种主要蛋白质，分子量分别为120、60和35 kDa，分别占总蛋白的70%、10%和20%。其他研究结果强烈表明，35 kDa的蛋白质可能是这些膜中的钙激活钾离子通道蛋白。
