Ion- and water-binding sites inside an occluded hourglass pore of a trimeric intracellular cation (TRIC) channel

BMC Biology

Research Article

Jianli Guo¹  Xiaomin Ou¹  Longfei Wang¹  Hanting Yang²  Zhenfeng Liu²  Xiuying Liu²  Jianyuan Sun³ 

[1] National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China;National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China;University of Chinese Academy of Sciences, Beijing, China;State Key Laboratory of Brain & Cognitive Sciences, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China;University of Chinese Academy of Sciences, Beijing, China;

关键词: Crystal structure;    Ion channel;    Membrane protein;    Selectivity;    Gating mechanism;   

DOI  :  10.1186/s12915-017-0372-8

 received in 2017-01-01, accepted in 2017-04-05,  发布年份 2017

来源: Springer

【 摘 要 】

BackgroundTrimeric intracellular cation (TRIC) channels are crucial for Ca2+ handling in eukaryotes and are involved in K+ uptake in prokaryotes. Recent studies on the representative members of eukaryotic and prokaryotic TRIC channels demonstrated that they form homotrimeric units with the ion-conducting pores contained within each individual monomer.ResultsHere we report detailed insights into the ion- and water-binding sites inside the pore of a TRIC channel from Sulfolobus solfataricus (SsTRIC). Like the mammalian TRIC channels, SsTRIC is permeable to both K+ and Na+ with a slight preference for K+, and is nearly impermeable to Ca2+, Mg2+, or Cl–. In the 2.2-Å resolution K+-bound structure of SsTRIC, ion/water densities have been well resolved inside the pore. At the central region, a filter-like structure is shaped by the kinks on the second and fifth transmembrane helices and two nearby phenylalanine residues. Below the filter, the cytoplasmic vestibule is occluded by a plug-like motif attached to an array of pore-lining charged residues.ConclusionsThe asymmetric filter-like structure at the pore center of SsTRIC might serve as the basis for the channel to bind and select monovalent cations. A Velcro-like plug-pore interacting model has been proposed and suggests a unified framework accounting for the gating mechanisms of prokaryotic and eukaryotic TRIC channels.

【 授权许可】

CC BY   
© Liu et al. 2017