Fig. 4: Crystal structure of SpaR.
From: Mirror proteorhodopsins

a Overall side view of the protein. Hydrophobic/hydrophilic membrane core boundaries are shown with grey horizontal lines. b The RSB region of SpaR. H-bonds in the region are shown with black dashed lines. c Detailed view of the cytoplasmic part of SpaR. H-bonds in the region are shown with black dashed lines. d Detailed view of the extracellular part of SpaR. Retinal is colored teal in all panels. The cavities are shown with pink surface.