(Left) A Clustal W alignment of helix B regions in reported ChRs from the following algal species (abbreviated by the first two or three letters in the sequence title): Chlamydomonas reinhardtii, Volvox carteri, Pleodorina starrii, C. raudensis, Platymonas subcordiformis, C. augustae, C. yellowstonensis, Haematococcus pluvialis, Dunaliella salina, Mesostigma viride, and Pyramimonas gelidicola. Lysine residues corresponding to Lys-132 (CrChR1/C1C2 numbering, because from the N-terminus to beyond the shown portion of the C1C2 derives from CrChR1) are highlighted yellow, and glutamate residues green. (Right) An overlay of photoactive site structures of BR (1c3w, yellow), NpSRII (1jgj, blue), and C1C2 ChR (3ug9, red) generated by DeepView software.