Bakteriorodopsin
caption: Bacteriorhodopsin is a trimer . Red line indicates extracellular side (EC) of the membrane
caption: Bacteriorhodopsin single monomer with retinal molecule between 7 vertical alpha helixes ( PDB ID: 1X0S [4] [5] [6] ). One more small helix is light blue, beta sheet yellow.
caption: Bacteriorhodopsin trimer with one retinal molecule in each subunit seen from the extracellular side EC ( PDB ID: 1X0S [4] [5] [6] ).