Bass Randal B, Strop Pavel, Barclay Margaret, Rees Douglas C
Division of Chemistry and Chemical Engineering, Biochemistry Option, Howard Hughes Medical Institute, Mail Code 114-96, California Institute of Technology, Pasadena, CA 91125, USA.
Science. 2002 Nov 22;298(5598):1582-7. doi: 10.1126/science.1077945.
The mechanosensitive channel of small conductance (MscS) responds both to stretching of the cell membrane and to membrane depolarization. The crystal structure at 3.9 angstroms resolution demonstrates that Escherichia coli MscS folds as a membrane-spanning heptamer with a large cytoplasmic region. Each subunit contains three transmembrane helices (TM1, -2, and -3), with the TM3 helices lining the pore, while TM1 and TM2, with membrane-embedded arginines, are likely candidates for the tension and voltage sensors. The transmembrane pore, apparently captured in an open state, connects to a large chamber, formed within the cytoplasmic region, that connects to the cytoplasm through openings that may function as molecular filters. Although MscS is likely to be structurally distinct from other ion channels, similarities in gating mechanisms suggest common structural elements.
小电导机械敏感通道（MscS）对细胞膜的拉伸和膜去极化均有反应。分辨率为3.9埃的晶体结构表明，大肠杆菌MscS折叠成具有大细胞质区域的跨膜七聚体。每个亚基包含三个跨膜螺旋（TM1、-2和-3），其中TM3螺旋排列在孔道内，而带有膜嵌入精氨酸的TM1和TM2可能是张力和电压传感器的候选者。跨膜孔道显然处于开放状态，连接到在细胞质区域内形成的一个大腔室，该腔室通过可能起分子过滤器作用的开口与细胞质相连。尽管MscS在结构上可能与其他离子通道不同，但其门控机制的相似性表明存在共同的结构元件。
