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Nat Commun. 2017 May 19;8:15103. doi: 10.1038/ncomms15103.

Structural basis for conductance through TRIC cation channels.

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State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
CAS Center for Excellence in Biomacromolecules, Beijing 100101, China.
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032, USA.
State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.
Center on Membrane Protein Production and Analysis, New York Structural Biology Center, 89 Convent Avenue, New York, New York 10027, USA.


Mammalian TRICs function as K+-permeable cation channels that provide counter ions for Ca2+ handling in intracellular stores. Here we describe the structures of two prokaryotic homologues, archaeal SaTRIC and bacterial CpTRIC, showing that TRIC channels are symmetrical trimers with transmembrane pores through each protomer. Each pore holds a string of water molecules centred at kinked helices in two inverted-repeat triple-helix bundles (THBs). The pores are locked in a closed state by a hydrogen bond network at the C terminus of the THBs, which is lost when the pores assume an open conformation. The transition between the open and close states seems to be mediated by cation binding to conserved residues along the three-fold axis. Electrophysiology and mutagenesis studies show that prokaryotic TRICs have similar functional properties to those of mammalian TRICs and implicate the three-fold axis in the allosteric regulation of the channel.

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