Open AccessMolecular understanding of calcium permeation through the open Orai channel
Author(s) -
Xiaofen Liu,
Gao Wu,
Yi Yu,
Xiaozhe Chen,
Renci Ji,
Jing Lü,
Xin Li,
Xing Zhang,
Xue Yang,
Yuequan Shen
Publication year - 2019
Publication title -
plos biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.127
H-Index - 271
eISSN - 1545-7885
pISSN - 1544-9173
DOI - 10.1371/journal.pbio.3000096
Subject(s) - permeation , biophysics , cytosol , membrane potential , ion channel , membrane , transmembrane protein , transmembrane domain , helix (gastropod) , biology , chemistry , biochemistry , enzyme , ecology , receptor , snail
The Orai channel is characterized by voltage independence, low conductance, and high Ca 2+ selectivity and plays an important role in Ca 2+ influx through the plasma membrane (PM). How the channel is activated and promotes Ca 2+ permeation is not well understood. Here, we report the crystal structure and cryo-electron microscopy (cryo-EM) reconstruction of a Drosophila melanogaster Orai (dOrai) mutant (P288L) channel that is constitutively active according to electrophysiology. The open state of the Orai channel showed a hexameric assembly in which 6 transmembrane 1 (TM1) helices in the center form the ion-conducting pore, and 6 TM4 helices in the periphery form extended long helices. Orai channel activation requires conformational transduction from TM4 to TM1 and eventually causes the basic section of TM1 to twist outward. The wider pore on the cytosolic side aggregates anions to increase the potential gradient across the membrane and thus facilitate Ca 2+ permeation. The open-state structure of the Orai channel offers insights into channel assembly, channel activation, and Ca 2+ permeation.