Extended Data Fig. 6: Conservation of the retinal-binding site.

a, Maximum conserved residues around retinal and their conservation ratios in HeR family members, with their residue numbers in HeR and BR. The variations of the amino acid species in TaHeR, HeR 48C12, and representative type-1 rhodopsins are shown in the lower part. b, Light-induced difference absorption spectra of wild-type (black curve) and 17 mutants (red curve) of HeR solubilized with DDM from E. coli membrane, in the presence of 500 mM hydroxylamine (HA). Positive and negative signals show the spectra before and after illuminations, corresponding to those of the rhodopsin and the retinal oxime, respectively. Mutant spectra were normalized to a positive peak at 542 nm in the case of the wild type, whereas the mutant spectra were multiplied by factors of 0.8–3.1, as shown in each graph. These experiments were performed once. c, The results of the mutagenesis effects mapped on the retinal-binding site.