Rhodopsin

Rhodopsin is a seven-helix transmembrane
protein with binding sites for functionally important
molecules such as transducin, rhodopsin
kinase, and arrestin on the cytosol side. The
binding site of the light-sensitive molecule
(chromophore) is lysine in position 296 of the
seventh transmembrane domain. The light-absorbing
group consists of 11-cis-retinal. The
amino end of rhodopsin is located in the disk interspaces,
and the carboxy end on the cytosol
side. About half of the molecule is contained in
the seven transmembrane hydrophobic domains,
one-fourth in the disk interspaces and
one-fourth on the cytosol side.