Zhao W, Sun M, Sun L, Liu Y, Yang Y, Huang L, Fan Y, Cheng X, Cao P, Hu Y, Li L, Tian Y, Wang R, Yu Y. A Highly Conserved Salt Bridge Stabilizes the Kinked Conformation of β2,3-Sheet Essential for Channel Function of P2X4 Receptors. Journal of Biological Chemistry. 2016 Apr;291(15):7990–8003. doi: 10.1074/jbc.m115.711127.