Sun Z P, Akabas M H, Goulding E H, Karlin A, Siegelbaum S A
Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
Neuron. 1996 Jan;16(1):141-9. doi: 10.1016/s0896-6273(00)80031-8.
In voltage-gated ion channels and in the homologous cyclic nucleotide-gated (CNG) channels, the loop between the S5 and S6 transmembrane segments (P region) is thought to form the lining of the pore. To investigate the structure and the role in gating of the P region of the bovine retinal CNG channel, we determined the accessibility of 11 cysteine-substituted P region residues to small, charged sulfhydryl reagents applied to the inside and outside of membrane patches in the open and closed states of the channel. The results suggest that the P region forms a loop that extends toward the central axis of the channel, analogous to the L3 loop of bacterial porin channels. Furthermore, the P region, in addition to forming the ion selectivity filter, functions as the channel gate, the structure of which changes when the channel opens.
在电压门控离子通道和同源环核苷酸门控（CNG）通道中，S5和S6跨膜片段之间的环（P区）被认为形成了孔道的内衬。为了研究牛视网膜CNG通道P区的结构及其在门控中的作用，我们测定了11个半胱氨酸取代的P区残基对应用于通道开放和关闭状态下膜片内外的带电荷小巯基试剂的可及性。结果表明，P区形成一个朝向通道中心轴延伸的环，类似于细菌孔蛋白通道的L3环。此外，P区除了形成离子选择性过滤器外，还作为通道门发挥作用，通道开放时其结构会发生变化。
