Properties of the Retinal Binding Site in Bacteriorhodopsin. Use of Retinol and Retinyl Moieties as Fluorescent Probes

The fluorescence spectra of various reduced bacteriorhodopsin chromophore species indicate energy transfer from aromatic amino acid side chains of the protein to the retinyl moiety. Binding studies with retinol reveal that energy transfer occurs only when the retinyl moiety is bound in the chromophoric site of the protein. Retroretinol is a fluorescent probe for the binding site.