Cartoons view of Bacteriorhodopsin colored by group. There are 7 transmembrane alpha;-helices. This fold is similar to the G-protein coupled receptors (e.g. rhodopsin)

Bacteriorhodopsin contains an essential prosthetic group, retinal, which is covalently linked to a Lysine in the seventh helix.

The phospholipids seen in this crystal form give a good indication of the boundaries of the bilayer.

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