Figure 7
Gate structure, open pore conformation and counterion configuration in Chrimson. (a) Schematic putative closed and open configuration of Chrimson. Closed: Non-conductive conformation of Chrimson that is stabilized by E1’ and E2’ in the inner gate, E300 in the central gate and E4’ in the outer gate. Open: Conductive conformation of Chrimson with a pore constriction and proton selectivity filter in the outer pore at E4’ and E5’ Inlet: Counterion configuration with a protonated retinal Schiff’base, protonated E165 and deprotonated D295. Mutants of all presented residues induce significant hypsochromic shifts, indicating an important role of displayed side chains in counterion configuration (F135A Δλmax = 50 ± 6 nm, E4’A Δλmax = 70 ± 5 nm, Y159A Δλmax = 39 ± 4 nm, E165A Δλmax = 20 ± 5 nm, D295A Δλmax = 61 ± 7 nm). (b) Comparison to the proposed configurations in CrChR2. Closed: Non-conductive conformation of CrChR2 that is stabilized by E1’ and R310 in the inner gate and E3’, S63 and N258 in the central gate. Open: Conductive state of CrChR2 with a pore constriction and proton selectivity filter in the center of the protein at E3’.
