Tryptophan fluorescence quenching as a monitor for the protein conformation changes occurring during the photocycle of bacteriorhodopsin under different perturbations.

Abstract

The step, leading to a proton-pumping process that increases the proton concentration on the outside surface of the membrane (7). The created proton gradient across the membrane is then used to transform ADP into ATP in the final step of the photosynthesis of bR (8). Thus, the understanding of the mechanism of the PSB deprotonation becomes important to our understanding of the molecular mechanism of solar energy storage in nature.bR normally contains bound Ca2' and Mg2+ (9, 10).Acidification or removal of metal cations from bR produces the purple-to-blue color transition (9-14). [15][16][17]. bR contains 8 tryptophan and 11 tyrosine residues out of a total of 248 amino acid residues in the bR polypeptide chain (23). These aromatic residues absorb at a relatively long wavelength (-280 nm) compared with the other amino acid residues. Optical probes of these amino acid residues have been used to understand the protein structure and the interactions of the protein with the retinal in bR and its photocycle intermediates (24-29). Protein fluorescence of bR and its retinal-free form, bacterioopsin, is characteristic of tryptophan fluorescence (30,31). The excitation of tyrosine may indirectly contribute to the tryptophan emission by energy transfer (32). Most of the tryptophan in bR interacts with the retinal in bR (28,29,31). The variation in the observed lifetimes of the tryptophan fluorescence decay components has been suggested (29) to result from the variation of the energy transfer efficiency between excited tryptophan molecules and the retinal in bR. Energy transfer from-tyrosine and tryptophan to the retinal in bR has a quantum yield of 0.7-0.8 and leads to a photocycle identical with that triggered by the excitation of the visible absorption bands of retinal (27).

Fluorescence spectroscopy of rhodopsins: Insights and approaches

“…Tryptophan fluorescence quenching was used as a monitor for protein conformation changes occurring during the photocycle of bR [90]. In particular, tryptophan fluorescence changes were observed upon formation of the M-intermediate [90]. A similar result was obtained in investigations of tryptophan fluorescence changes upon formation of the MII state in visual rhodopsin [69].…”

“…Tryptophan fluorescence quenching was used as a monitor for protein conformation changes occurring during the photocycle of bR [90]. In particular, tryptophan fluorescence changes were observed upon formation of the M-intermediate [90].…”

Sensors and Analytical Technologies for Air Quality: Particulate Matters and Bioaerosols

“…[40] Microfluidic chip can also be coupled with fluorescent immunoassay for Mycobacterium tuberculosis and with high-throughput LAMP analysis for aerosolized bacteria. [41,42]…”

Effects of tryptophan mutation on the deprotonation and reprotonation kinetics of the Schiff base during the photocycle of bacteriorhodopsin

“…Upon absorption of light, the light adapted bR undergoes a photocycle that involves a number of spectroscopically distinct intermediates: bR560 -_ K610 -> L5 M42-> N520 -064-bR560 bR contains 8 tryptophan residues out of a total 248 amino acid residues in its polypeptide chain (2). The possible involvement of tryptophan residues in bR proton pumping has been studied by several different techniques (3)(4)(5)(6)(7)(8). Fluorescence quenching upon retinal binding revealed that most of tryptophans in bR interact with the retinal chromophore (4)(5)(6).…”

“…A time-resolved fluorescence study has detected the photolysis-induced changes in the fluorescence intensity during the lifetime of L and M intermediates, indicating that some of tryptophan residues undergo a change in environment in the vicinity of the retinal chromophore (7). Furthermore, a tryptophan fluorescence quenching study of different perturbations on bR such as deionization and delipidation has shown that different protein conformation changes may occur during the photocycle of bR under these perturbations (8). Recently, it has been Tatsushi Mogi's present address is Department of Biology, Faculty of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan.…”