Miller C
Graduate Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02254.
Neuron. 1988 Dec;1(10):1003-6. doi: 10.1016/0896-6273(88)90157-2.
Single high-conductance Ca2(+)-activated K+ channels were incorporated into planar lipid bilayers, and the discrete block by charybdotoxin (CTX), a protein inhibitor of this channel, was studied. In particular, the effect of externally added tetraethylammonium (TEA) on CTX blocking kinetics was investigated. TEA decreases the on-rate of CTX in exact proportion to its blocking of the single-channel current. The CTX off-rate is unaffected by TEA. The results demonstrate that TEA and CTX are mutually exclusive in their binding to the channel. Since the site of TEA binding is known to be located on the external side of the conduction pore, this result further strengthens the proposal that the CTX binding site is located in the external mouth of the channel.
将单个高电导钙激活钾通道整合到平面脂质双分子层中，研究了该通道的蛋白抑制剂蝎毒素（CTX）对其的离散阻断作用。特别研究了外部添加的四乙铵（TEA）对CTX阻断动力学的影响。TEA降低CTX的结合速率，其降低比例与它对单通道电流的阻断比例完全相同。TEA不影响CTX的解离速率。结果表明，TEA和CTX在与通道的结合上相互排斥。由于已知TEA的结合位点位于传导孔的外侧，这一结果进一步支持了CTX结合位点位于通道外口的观点。
