Fig. 1: Structural and functional comparison of CrChR2 and GtACR1.

a Structural alignment of the central constriction site residues of CrChR2 (green amino acid carbon atoms) from PDB-ID 6EID²¹ and GtACR1 (gray amino acid carbon atoms) from PDB-ID 6EDQ²². The retinal (black carbon atoms) is taken from GtACR1. Nitrogen atoms are colored blue and oxygen atoms red. b Photocurrents of CrChR2 WT and GtACR1 WT. The shown photocurrents are a response of CrChR2 and GtACR1 (data replotted from Govorunova et al.⁴⁸, Fig. 1D12) to a 1 s light pulse at a holding potential of −60 mV in HEK293FT cells 10–19 days after transfection. CrChR2 shows the characteristic decay of the photocurrent upon continuous illumination. GtACR1 produces a significantly larger photocurrent compared to CrChR2 and does not display the described inactivation of the photocurrent. However, channel closing is much slower in GtACR1 compared to CrChR2. c Photocurrents of GtACR1 WT and GtACR1 Q46E (data replotted from Kim et al.⁵⁵, Extended Data Fig. 8). The shown photocurrents are a response to a 1.5 s light pulse in patch-clamp recordings of HEK293 cells 24–48 h after transfection. The GtACR1 WT shows a significantly larger photocurrent compared to the GtACR1 variant Q46E. Furthermore, GtACR1 Q46E exhibits strong current attenuation.