Fig. 3: Ion pores of KnChR and CrChR2.

a Water accessible cavities are illustrated in the KnChR structure, showing the putative ion pathway. The three constriction sites for the inner, central, and extracellular gates are enclosed within squares. Water molecules are indicated by red spheres. b Comparison of the constriction sites of KnChR (left panels) and CrChR2 (PDB ID: 6EID) (right panels), for the inner (upper panels), central (middle panels), and outer (lower panels) gates. The constituent residues are shown as sticks. Water molecules are indicated by red spheres. Black dashed lines indicate hydrogen bonds. c Representative photocurrent traces of the C-terminal truncated variant of KnChR (KnChR-272) and mutants. We used KnChR-272 as a template for the mutant, because KnChR-272 exhibits higher channel activity than KnChR-697 owing to the absence of the C-terminal region. The cells were illuminated with light (λ = 470 nm) during the time indicated by blue bars. The membrane voltage was clamped from −60 to +40 mV for every 20-mV step. d Comparison of photocurrent amplitudes of KnChR-272 and mutants at −60 mV. In the bar graph, gray bars indicate the amplitude from the peak photocurrent (Ip), and open bars indicate the amplitude from the steady-state photocurrent (Iss). n = 6 cells. Source data are provided as a Source Data file. e The channel-closing kinetics of KnChR-272 and mutants after illumination cessation (τ-off) at −60 mV. n = 6 cells. All data in (d, e) are expressed as mean ± SEM and were evaluated with the Mann-Whitney U test for statistical significance. It was judged as statistically insignificant when p > 0.05. *p < 0.05, **p < 0.01 *** p < 0.005. Source data are provided as a Source Data file.