Uysal Serdar, Vásquez Valeria, Tereshko Valentina, Esaki Kaori, Fellouse Frederic A, Sidhu Sachdev S, Koide Shohei, Perozo Eduardo, Kossiakoff Anthony
Department of Biochemistry and Molecular Biology, and Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA.
Proc Natl Acad Sci U S A. 2009 Apr 21;106(16):6644-9. doi: 10.1073/pnas.0810663106. Epub 2009 Apr 3.
KcsA is a proton-activated, voltage-modulated K(+) channel that has served as the archetype pore domain in the Kv channel superfamily. Here, we have used synthetic antigen-binding fragments (Fabs) as crystallographic chaperones to determine the structure of full-length KcsA at 3.8 A, as well as that of its isolated C-terminal domain at 2.6 A. The structure of the full-length KcsA-Fab complex reveals a well-defined, 4-helix bundle that projects approximately 70 A toward the cytoplasm. This bundle promotes a approximately 15 degree bending in the inner bundle gate, tightening its diameter and shifting the narrowest point 2 turns of helix below. Functional analysis of the full-length KcsA-Fab complex suggests that the C-terminal bundle remains whole during gating. We suggest that this structure likely represents the physiologically relevant closed conformation of KcsA.
KcsA是一种质子激活、电压调节的钾离子通道，它是Kv通道超家族中孔结构域的原型。在此，我们使用合成抗原结合片段（Fabs）作为晶体学伴侣，以3.8埃的分辨率确定全长KcsA的结构，以及以2.6埃的分辨率确定其分离的C末端结构域的结构。全长KcsA-Fab复合物的结构揭示了一个明确的4螺旋束，该螺旋束向细胞质方向突出约70埃。这个螺旋束促使内部束门产生约15度的弯曲，收紧其直径并将最窄点向下移动2圈螺旋。对全长KcsA-Fab复合物的功能分析表明，C末端螺旋束在门控过程中保持完整。我们认为这种结构可能代表了KcsA生理相关的关闭构象。
