Moore H P, Hartig P R, Raftery M A
Proc Natl Acad Sci U S A. 1979 Dec;76(12):6265-9. doi: 10.1073/pnas.76.12.6265.
Membrane vesicles containing partially inactivated acetylcholine receptor (AcChoR) channels may produce a full 22Na+ flux response because an excess of channels may exist above the level needed to completely empty the vesicles of ions. Therefore, attempts to use ion flux amplitudes as indicators of AcChoR function may fail due to the presence of these excess AcChoR channels. Random inactivation of variable fractions of AcChoR channels in vesicles by the irreversible binding of the neurotoxin alpha-bungarotoxin provides a tool for assessing the size of the excess receptor population. Using this approach, we predict that the dependence of the flux response on partial inactivation by alpha-bungarotoxin will drastically change if an essential AcChoR component is substantially removed from the membranes. Membranes from which Mr 43,000, Mr 90,000, and other polypeptides had been substantially removed by base extraction exhibited a flux response after random inactivation that was indistinguishable from that of untreated membranes. Therefore, those components which are substantially removed by base extraction do not appear to be essential for AcChoR-mediated ion flux.
含有部分失活的乙酰胆碱受体(AcChoR)通道的膜泡可能会产生完整的22Na+通量响应,因为可能存在超过使膜泡中的离子完全排空所需水平的过量通道。因此,由于这些过量的AcChoR通道的存在,试图将离子通量幅度用作AcChoR功能指标的尝试可能会失败。通过神经毒素α-银环蛇毒素的不可逆结合使膜泡中可变比例的AcChoR通道随机失活,为评估过量受体群体的大小提供了一种工具。使用这种方法,我们预测,如果从膜中大量去除必需的AcChoR成分,通量响应对α-银环蛇毒素部分失活的依赖性将发生巨大变化。通过碱提取大量去除了43000道尔顿、90000道尔顿和其他多肽的膜,在随机失活后表现出与未处理膜无法区分的通量响应。因此,那些通过碱提取大量去除的成分似乎对AcChoR介导的离子通量不是必需的。