Fig. 4

Phylogeny and absorption spectrum of Platynereis c-opsin2. a Phylogenetic tree showing Platynereis c-opsin2 grouped with other ciliary opsins (see also Additional file 6). Bootstrap values are shown in percent (of 1000 bootstraps), bootstraps less than 50 and not pertaining directly to c-opsin2 are omitted. b Absorption spectrum of Platynereis c-opsin2 purified from COS-1 cells after incubation with 11-cis-retinal (black (1)). Spectra after repeated stimulation for 1 min by 440 nm light (red (2), yellow (4)) and for 30 s at > 580 nm (blue (3), purple (5)) are also shown as traces. The absorption maximum at ~490 nm is highlighted in green. (Inset) The absorption spectrum of Platynereis c-opsin2 in a wider wavelength range. Robust absorbance at ~280 nm is attributed to misfolded protein species