Rhodopsin's secondary structure revisited : assignment of structural elements

Abstract FT-IR spectroscopy has been applied to study the secondary structure of rhodopsin in dehydrated films of bovine rod photoreceptor membranes. Curve fitting analysis of the amide I band around 1658 cm −1 compares well with data obtained from samples in the hydrated state. Repeating this analysis on samples, treated with proteinase K or thermolysin, secondary structural elements at the cytoplasmic side of the photoreceptor membrane can be located. We present evidence for the location of a a β-sheet and a β-turn near the lipid anchor in the C-terminal region of the protein, and for an α-helical structure in the third cytoplasmic loop.