Ramanathan R, Saimi Y, Peterson J B, Nelson D L, Kung C
J Cell Biol. 1983 Nov;97(5 Pt 1):1421-8. doi: 10.1083/jcb.97.5.1421.
Immobilization of Paramecium followed the binding of antibodies to the major proteins of the ciliary membrane (the immobilization antigens, i-antigens, approximately 250,000 mol wt). Immunoelectron microscopy showed this binding to be serotype-specific and to occur over the entire cell surface. Antibody binding also reduced the current through the Ca-channel of the excitable ciliary membrane as monitored using a voltage-clamp. The residual Ca-current appeared normal in its voltage sensitivity and kinetics. As a secondary consequence of antibody binding, the Ca-induced K-current was also reduced. The resting membrane characteristics and other activatable currents, however, were not significantly altered by the antibody treatment. Since monovalent fragments of the antibodies also reduced the current but did not immobilize the cell, the electrophysiological effects were not the secondary consequences of immobilization. Antibodies against the second most abundant family of proteins (42,000-45,000 mol wt) had similar electrophysiological effects as revealed by experiments in which the Paramecia and the serum were heterologous with respect to the i-antigen but homologous with respect to the 42,000-45,000-mol-wt proteins. Protease treatment, shown to remove the surface antigen, also caused a reduction of the Ca-inward current. The loss of the inward Ca-current does not seem to be due to a drop in the driving force for Ca++ entry since increasing the external Ca++ or reducing the internal Ca++ (through EGTA injection) did not restore the current. Here we discuss the possibilities that (a) the major proteins define the functional environment of the Ca-channel and that (b) the Ca-channel is more susceptible to certain general changes in the membrane.
草履虫的固定化是在抗体与纤毛膜的主要蛋白质（固定化抗原，i抗原，分子量约250,000）结合之后发生的。免疫电子显微镜显示这种结合具有血清型特异性，并且发生在整个细胞表面。使用电压钳监测发现，抗体结合还降低了可兴奋纤毛膜上钙通道的电流。残余的钙电流在电压敏感性和动力学方面看起来正常。作为抗体结合的次要结果，钙诱导的钾电流也降低了。然而，静息膜特性和其他可激活电流并未因抗体处理而发生显著改变。由于抗体的单价片段也降低了电流，但并未使细胞固定化，因此电生理效应不是固定化的次要结果。针对第二丰富的蛋白质家族（分子量42,000 - 45,000）的抗体具有类似的电生理效应，这在实验中得到了揭示，在这些实验中，草履虫和血清在i抗原方面是异源的，但在分子量42,000 - 45,000的蛋白质方面是同源的。蛋白酶处理显示可去除表面抗原，也导致内向钙电流降低。内向钙电流的丧失似乎不是由于钙离子进入的驱动力下降，因为增加外部钙离子或减少内部钙离子（通过注射乙二醇双乙醚二胺四乙酸）并不能恢复电流。在此我们讨论以下可能性：（a）主要蛋白质定义了钙通道的功能环境；（b）钙通道对膜的某些一般变化更敏感。
