Structural, Biochemical, and Functional Characterization of the Cyclic Nucleotide Binding Homology Domain from the Mouse EAG1 Potassium Channel
Structural, Biochemical, and Functional Characterization of the Cyclic Nucleotide Binding Homology Domain from the Mouse EAG1 Potassium Channel
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DOI：
10.1016/j.jmb.2012.06.025
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发表时间：
2012-10-12
影响因子：
5.6
通讯作者：
Morais-Cabral, Joao H.
中科院分区：
文献类型：
--
作者：
Marques-Carvalho, Maria J.;Sahoo, Nirakar;Morais-Cabral, Joao H.
KCNH通道是具有重要生理功能的电压门控性钾通道。在这些通道中，被称为环核苷酸结合同源性（CNB-同源性）结构域的C-末端胞质区域显示出与环核苷酸结合（CNB）结构域的强序列相似性。然而，分离的结构域不结合环核苷酸。在这里，我们报告的X-射线结构的CNB同源结构域从小鼠EAG 1通道。通过与最近确定的来自斑马鱼ELK（eag-like K+）通道的CNB同源结构域和来自MlotiK 1和HCN（hyperpolarization-activated cyclic nucleotide-gated）钾通道的CNB结构域的结构比较，我们建立了CNB同源结构域的结构特征，其解释了对环核苷酸的低亲和力。我们的结构建立了“自配体”构象，其中结构域的C-末端的两个残基在等同位置结合到CNB结构域中的环核苷酸，是CNB同源结构域的保守特征。重要的是，我们提供的生化证据表明，也有一个unliganded构象的C-末端的域剥离远离其结合位置。这种unliganded构象的功能表征揭示了CNB-同源结构域在通道门控中的作用。(c)2012爱思唯尔有限公司保留所有权利。
KCNH channels are voltage-gated potassium channels with important physiological functions. In these channels, a C-terminal cytoplasmic region, known as the cyclic nucleotide binding homology (CNB-homology) domain displays strong sequence similarity to cyclic nucleotide binding (CNB) domains. However, the isolated domain does not bind cyclic nucleotides. Here, we report the X-ray structure of the CNB-homology domain from the mouse EAG1 channel. Through comparison with the recently determined structure of the CNB-homology domain from the zebrafish ELK (eag-like K+) channel and the CNB domains from the MlotiK1 and HCN (hyperpolarization-activated cyclic nucleotide-gated) potassium channels, we establish the structural features of CNB-homology domains that explain the low affinity for cyclic nucleotides. Our structure establishes that the "self-liganded" conformation, where two residues of the C-terminus of the domain are bound in an equivalent position to cyclic nucleotides in CNB domains, is a conserved feature of CNB-homology domains. Importantly, we provide biochemical evidence that suggests that there is also an unliganded conformation where the C-terminus of the domain peels away from its bound position. A functional characterization of this unliganded conformation reveals a role of the CNB-homology domain in channel gating. (c) 2012 Elsevier Ltd. All rights reserved.