Zhou Yu, Xia Xiao-Ming, Lingle Christopher J
Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110
Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110.
Proc Natl Acad Sci U S A. 2015 Apr 21;112(16):5237-42. doi: 10.1073/pnas.1500953112. Epub 2015 Apr 6.
To probe structure and gating-associated conformational changes in BK-type potassium (BK) channels, we examined consequences of Cd(2+) coordination with cysteines introduced at two positions in the BK inner pore. At V319C, the equivalent of valine in the conserved Kv proline-valine-proline (PVP) motif, Cd(2+) forms intrasubunit coordination with a native glutamate E321, which would place the side chains of V319C and E321 much closer together than observed in voltage-dependent K(+) (Kv) channel structures, requiring that the proline between V319C and E321 introduces a kink in the BK S6 inner helix sharper than that observed in Kv channel structures. At inner pore position A316C, Cd(2+) binds with modest state dependence, suggesting the absence of an ion permeation gate at the cytosolic side of BK channel. These results highlight fundamental structural differences between BK and Kv channels in their inner pore region, which likely underlie differences in voltage-dependent gating between these channels.
为了探究BK型钾（BK）通道的结构以及与门控相关的构象变化，我们研究了镉离子（Cd(2+)）与BK通道内孔两个位置引入的半胱氨酸配位的结果。在V319C处，它相当于保守的Kv脯氨酸-缬氨酸-脯氨酸（PVP）基序中的缬氨酸，Cd(2+)与天然谷氨酸E321形成亚基内配位，这会使V319C和E321的侧链比在电压依赖性钾（Kv）通道结构中观察到的靠得更近，这就要求V319C和E321之间的脯氨酸在BK S6内螺旋中引入比在Kv通道结构中观察到的更尖锐的扭结。在内孔位置A316C处，Cd(2+)以适度的状态依赖性结合，这表明BK通道胞质侧不存在离子渗透门。这些结果突出了BK通道和Kv通道在内孔区域的基本结构差异，这可能是这些通道电压依赖性门控差异的基础。
