The structure of the prokaryotic cyclic nucleotide-modulated potassium channel MloK1 at 16 A resolution |
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Authors: | Chiu Po-Lin Pagel Matthew D Evans James Chou Hui-Ting Zeng Xiangyan Gipson Bryant Stahlberg Henning Nimigean Crina M |
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Institution: | Molecular and Cellular Biology, College of Biological Sciences, University of California-Davis, 1 Shields Avenue, Davis, CA 95616, USA. |
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Abstract: | 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. |
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