Fig. 5: Detailed view of the cytoplasmic and extracellular parts of the rhodopsins.
From: Mirror proteorhodopsins

Detailed view of the cytoplasmic part of (a) SpaR; (b) BR; (c) ChR2. Detailed view of the extracellular part of (d) SpaR; (e) BR; (f) ChR2. Retinal cofactor is colored teal. The cavities are shown with pink surface. The central amino acid residues at the cytoplasmic side of the proteins (H37, D96, and H134) are colored orange.