Chiu Po-Lin, Pagel Matthew D, Evans James, Chou Hui-Ting, Zeng Xiangyan, Gipson Bryant, Stahlberg Henning, Nimigean Crina M
Molecular and Cellular Biology, College of Biological Sciences, University of California-Davis, 1 Shields Avenue, Davis, CA 95616, USA.
Structure. 2007 Sep;15(9):1053-64. doi: 10.1016/j.str.2007.06.020.
The gating ring of cyclic nucleotide-modulated channels is proposed to be either a two-fold symmetric dimer of dimers or a four-fold symmetric tetramer based on high-resolution structure data of soluble cyclic nucleotide-binding domains and functional data on intact channels. We addressed this controversy by obtaining structural data on an intact, full-length, cyclic nucleotide-modulated potassium channel, MloK1, from Mesorhizobium loti, which also features a putative voltage-sensor. We present here the 3D single-particle structure by transmission electron microscopy and the projection map of membrane-reconstituted 2D crystals of MloK1 in the presence of cAMP. Our data show a four-fold symmetric arrangement of the CNBDs, separated by discrete gaps. A homology model for full-length MloK1 suggests a vertical orientation for the CNBDs. The 2D crystal packing in the membrane-embedded state is compatible with the S1-S4 domains in the vertical "up" state.
基于可溶性环核苷酸结合结构域的高分辨率结构数据以及完整通道的功能数据，有人提出环核苷酸调节通道的门控环是由二聚体组成的二重对称二聚体或四重对称四聚体。我们通过获取来自百脉根中生根瘤菌的完整、全长环核苷酸调节钾通道MloK1的结构数据来解决这一争议，该通道还具有一个假定的电压传感器。我们在此展示了通过透射电子显微镜获得的MloK1的三维单颗粒结构以及在存在cAMP的情况下膜重构二维晶体的投影图。我们的数据显示CNBD呈四重对称排列，由离散的间隙隔开。全长MloK1的同源模型表明CNBD呈垂直方向。膜嵌入状态下的二维晶体堆积与垂直“向上”状态下的S1 - S4结构域兼容。
