Akabas M H, Stauffer D A, Xu M, Karlin A
Department of Physiology, College of Physicians and Surgeons, Columbia University, New York, NY 10032.
Science. 1992 Oct 9;258(5080):307-10. doi: 10.1126/science.1384130.
In order to understand the structural bases of ion conduction, ion selectivity, and gating in the nicotinic acetylcholine receptor, mutagenesis and covalent modification were combined to identify the amino acid residues that line the channel. The side chains of alternate residues--Ser248, Leu250, Ser252, and Thr254--in M2, a membrane-spanning segment of the alpha subunit, are exposed in the closed channel. Thus alpha 248-254 probably forms a beta strand, and the gate is closer to the cytoplasmic end of the channel than any of these residues. On channel opening, Leu251 is also exposed. These results lead to a revised view of the closed and open channel structures.
为了理解烟碱型乙酰胆碱受体中离子传导、离子选择性和门控的结构基础，将诱变和共价修饰相结合以鉴定构成通道内壁的氨基酸残基。α亚基跨膜片段M2中交替出现的残基——Ser248、Leu250、Ser252和Thr254——的侧链在关闭的通道中暴露。因此，α248 - 254可能形成一条β链，并且门控比这些残基中的任何一个更靠近通道的胞质端。在通道开放时，Leu251也会暴露。这些结果导致了对关闭和开放通道结构的修正观点。
