Article Figures & Data
Figures
- FIG 1
(A) Photoelectric response in a suspension of native cells of Mesostigma viride. Unilateral excitation with a 6-ns laser pulse at 530 nm. (B) Fluence-response dependence of the photoreceptor current. Excitation was with a 520 ± 20-nm light from a photoflash. (C) Action spectrum of the photoreceptor current in native M. viride cells. Solid line, Gaussian fit of the main peak; maximum, 531 nm; half-bandwidth, ~93 nm (for details, see the text). rel. u., relative units.
- FIG 2
(A) Phylogenetic tree of the channelrhodopsin family constructed by the neighbor-joining method; (B) alignment of channelrhodopsin sequences (regions of predicted helices B and C of the 7TM domain). The conserved Glu residues are shown in green, the conserved His residue at the proton donor position in BR (Asp96) is shown in blue, other conserved residues of the retinal binding pocket are shown in yellow, and important residues that are not conserved in MChR1 are shown in red.
- FIG 3
(A) Photocurrents in HEK293 cells expressing the 7TM domain of MChR1 recorded by the whole-cell patch clamp method at different holding potentials changed in 20-mV steps from −100 mV (the bottom trace) to +40 mV (the top trace). (B) Current voltage dependence of the peak photocurrent. Data are mean values ± SEM of results from four successive scans.
- FIG 4
(A) Photocurrents in HEK293 cells expressing the 7TM domain of MChR1 recorded by the whole-cell patch clamp method. Excitation was at 530 nm for 2 s, with a 30-s dark interval; relative light intensities, starting from the bottom trace, were 100%, 20%, 7%, 3%, and 0.5%. (B) Dependence of the amplitudes of the peak and plateau currents (filled squares and filled circles, respectively) and the initial slope of photocurrent (open squares) on the light intensity. The initial slope of the photocurrent was normalized to the peak value at the maximal intensity.
- FIG 5
Low-light-intensity action spectra of photoelectric responses in HEK293 cells. (A) MChR1 at the external pHs of 9.0 (filled squares), 7.4 (open circles), and 5.3 (open triangles). As these data were very close, a single B-spline solid line was drawn through the average values at each wavelength. (B) VChR1 at external pHs of 7.4 (filled squares) and 5.3 (open circles). Data for each spectrum are mean values ± SEM of results from 6 to 10 successive scans in opposite directions obtained on 2 to 3 cells.
- FIG 6
Current kinetics (A) and dependence of the rate of the fast-decay component on external pH (mean values ± SEM of results from 6 to 10 cells for each pH value) (B) of MChR1 and VChR1 (filled squares and open circles, respectively) expressed in HEK293 cells. Excitation was at 530 nm for 2 s. In panel A, time zero corresponds to the end of the light pulse.
- FIG 7
(A) Photoresponses generated by MChR1 and VChR1 expressed in HEK293 cells upon 25-Hz stimulation with 530-nm light; (B) dependence of the amplitude of modulation on the stimulus frequency for MChR1 (filled squares) and VChR1 (open circles). Data are the mean values ± SEM of results from 8 successive frequency changes in the opposite directions.
- FIG 8
Photocurrents generated by the A116E and C147A mutants and wild-type MChR1 (WT) in HEK293 cells. Traces were normalized at the plateau level to reveal the differences in the decay kinetics. The increased level of the noise reflects a decrease in the absolute current amplitudes. Excitation was at 530 nm for 0.5 s. Time zero corresponds to the end of the light pulse.
