Involvement of glutamate 97 in ion influx through photo-activated channelrhodopsin-2

► The possibility that the residue E97 of ChR2 is involved in ion flux is tested. ► The charge at this position strongly influenced the ion permeation. ► The charge replacement retarded the Gd3+-dependent channel block. ► The E97 would interact with a permeating cation to facilitate the dehydration. ► It is also a primary binding site of Gd3+ in the outer pore region of the channel.