Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA.
Proc Natl Acad Sci U S A. 2011 Jul 19;108(29):11896-9. doi: 10.1073/pnas.1105112108. Epub 2011 Jul 5.
Using a constitutively active channel mutant, we solved the structure of full-length KcsA in the open conformation at 3.9 Å. The structure reveals that the activation gate expands about 20 Å, exerting a strain on the bulge helices in the C-terminal domain and generating side windows large enough to accommodate hydrated K(+) ions. Functional and spectroscopic analysis of the gating transition provides direct insight into the allosteric coupling between the activation gate and the selectivity filter. We show that the movement of the inner gate helix is transmitted to the C-terminus as a straightforward expansion, leading to an upward movement and the insertion of the top third of the bulge helix into the membrane. We suggest that by limiting the extent to which the inner gate can open, the cytoplasmic domain also modulates the level of inactivation occurring at the selectivity filter.
我们使用组成型激活通道突变体，以 3.9Å 的分辨率解析了全长 KcsA 处于开放构象的结构。该结构揭示了激活门扩大了约 20Å，对 C 端结构域中的凸起螺旋施加了张力，并产生了足够大的侧窗，可容纳水合的 K(+)离子。门控跃迁的功能和光谱分析为激活门和选择性过滤器之间的变构偶联提供了直接的见解。我们表明，内门螺旋的运动作为直接的扩展传递到 C 端，导致向上运动和凸起螺旋的上三分之一插入到膜中。我们认为，通过限制内门可以打开的程度，细胞质结构域也可以调节选择性过滤器处发生的失活程度。
