CryoEM structure of a prokaryotic cyclic nucleotide-gated ion channel
CryoEM structure of a prokaryotic cyclic nucleotide-gated ion channel
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DOI：
10.1073/pnas.1700248114
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发表时间：
2017-04-25
影响因子：
11.1
通讯作者：
Veesler, David
中科院分区：
文献类型：
--
作者：
James, Zachary M.;Borst, Andrew J.;Veesler, David
环核苷酸门控（CNG）和超极化激活的环核苷酸调节（HCN）离子通道在光传导、嗅觉和心脏起搏中起着重要的生理作用。这些通道的特征在于存在羧基末端环核苷酸结合结构域（CNBD），其通过C-接头结构域连接至通道孔。虽然环核苷酸结合已被证明可以促进CNG和HCN通道开放，但门控的确切机制仍然知之甚少。在这里，我们使用cryoEM来确定的完整的LliK CNG通道的结构分离自Leptospira licerasiae-which股份序列相似性真核CNG和HCN通道-在饱和浓度的cAMP的存在下。短的S4-S5接头连接附近的电压敏感和孔结构域，以产生非结构域交换的跨膜结构，这似乎是该通道家族的标志。我们还观察到LliK C-接头和CNBD相对于分离的C-接头/CNBD片段的晶体结构和相关CNG、HCN和KCNH通道的cryoEM结构的主要构象变化。我们的LliK结构的构象可能代表在以前的研究中没有捕获的这个通道家族的功能状态。
Cyclic nucleotide-gated (CNG) and hyperpolarization-activated cyclic nucleotide-regulated (HCN) ion channels play crucial physiological roles in phototransduction, olfaction, and cardiac pace making. These channels are characterized by the presence of a carboxylterminal cyclic nucleotide-binding domain (CNBD) that connects to the channel pore via a C-linker domain. Although cyclic nucleotide binding has been shown to promote CNG and HCN channel opening, the precise mechanism underlying gating remains poorly understood. Here we used cryoEM to determine the structure of the intact LliK CNG channel isolated from Leptospira licerasiae-which shares sequence similarity to eukaryotic CNG and HCN channels-in the presence of a saturating concentration of cAMP. A short S4-S5 linker connects nearby voltage-sensing and pore domains to produce a non-domain-swapped transmembrane architecture, which appears to be a hallmark of this channel family. We also observe major conformational changes of the LliK C-linkers and CNBDs relative to the crystal structures of isolated C-linker/CNBD fragments and the cryoEM structures of related CNG, HCN, and KCNH channels. The conformation of our LliK structure may represent a functional state of this channel family not captured in previous studies.