Photochemical cycle of bacteriorhodopsin studied by resonance Raman spectroscopy
- 1 October 1979
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 18 (22) , 4886-4900
- https://doi.org/10.1021/bi00589a017
Abstract
Individual species of the photochemical cycle of bacteriorhodopsin, a retinal.sbd.protein complex of halobacteria, were studied in aqueous suspensions of the purple membrane at room temperature by resonance Raman (RR) spectroscopy with flow systems. Two pronounced deuterium shifts were found in the RR spectra of the all-trans complex BR-570 in H2O.sbd.D2O suspensions. The first is ascribed to C.dbd.NH+ (c.dbd.ND+) stretching vibrations of the protonated Schiff base which links retinal to opsin. The second is assigned tentatively to an X.sbd.H (X-D) bending mode, where X is an atom which carries an exchangeable proton. A RR spectrum of the 13-cis-retinal complex BR-548 could be deduced from spectra of the dark-adapted purple membrane. The RR spectrum of the M-412 intermediate was monitored in a double-beam pump.sbd.probe experiment. The main vibrational features of the intermediate M'' in the reaction .**GRAPHIC**. could be deduced from a photostationary mixture of M-412 and M''. Difference procedures were applied to obtained RR spectra of the L-550 intermediate and of 2 new long-lived species, R1''-590 and R2-550. From kinetic data it is suggested that R1''-590 and R2-550. From kinetic data it is suggested that R1''-590 links the proton-translocating cycle to the 13-cis cycle of BR-548. The protonation and isomeric states of the different species are discussed in light of the new spectroscopic and kinetic data. Conformational changes during the photochemical cycle play an important role.This publication has 2 references indexed in Scilit:
- Ultraviolet and visible absorption spectra of the purple membrane protein and the photocycle intermediatesBiochemistry, 1978
- The quantum efficiency of the bacteriorhodopsin photocycleBiophysical Journal, 1977