Saturation transfer EPR spectroscopy is used to study the photoinduced conformational changes of spin-labeled (Cys140 and Cys316) rhodopsin in a photoreceptor membrane. Illumination of rhodopsin with "yellow" light (λ > 450 nm), converting it from the dark form into metarhodopsin II, a physiologically active form, is accompanied by an increase in the mobility of the cytoplasmic loop (Cys140) and eighth alpha-helix (Cys316), whereas the subsequent illumination with "blue" light (λ < 445 nm), which converts metarhodopsin II into a mixture of inactive photoregenerated products, results in a decrease in the mobility. The restoration of the specific features of the photoinduced changes in the conformational mobility of the cytoplasmic loops of rhodopsin regenerated in the dark is demonstrated.
- EPR spectroscopy of spin labels
- Photoinduced conformational changes