Ion- and water-binding sites inside an occluded hourglass pore of a trimeric intracellular cation (TRIC) channel
Posted on 2017-04-22 - 05:00
Abstract Background Trimeric 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. Results Here 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 Clâ. In the 2.2-Ă
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. Conclusions The 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.
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Ou, Xiaomin; Guo, Jianli; Wang, Longfei; Yang, Hanting; Liu, Xiuying; Sun, Jianyuan; et al. (2017). Ion- and water-binding sites inside an occluded hourglass pore of a trimeric intracellular cation (TRIC) channel. figshare. Collection. https://doi.org/10.6084/m9.figshare.c.3749450.v1
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AUTHORS (7)
XO
Xiaomin Ou
JG
Jianli Guo
LW
Longfei Wang
HY
Hanting Yang
XL
Xiuying Liu
JS
Jianyuan Sun
ZL
Zhenfeng Liu