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Effect of Substitution of Proline‐77 to Aspartate on the Light‐Driven Proton Release of Bacteriorhodopsin
Author(s) -
Wang Yazhuo,
Zhao Yingchun,
Ming Ming,
Wu Jia,
Huang Weida,
Ding Jiandong
Publication year - 2012
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2012.01146.x
Subject(s) - bacteriorhodopsin , proton , aspartic acid , chemistry , proline , extracellular , residue (chemistry) , kinetics , proton pump , biophysics , stereochemistry , biochemistry , amino acid , biology , physics , enzyme , atpase , quantum mechanics , membrane
Wild‐type bacteriorhodopsin (BR) and another retinal protein archaerhodopsin 4 (AR4) are both light‐driven proton pumps, but exhibit opposite temporal orders of proton release and uptake upon a flash illumination at neutral pH due to a higher p K a of proton release complex (PRC) in AR4. Since the 77th residue in the extracellular side is proline (P) in BR, but aspartic acid (D) in AR4, we have mutated P77 in BR by D in this study. The new point mutation was found to affect the kinetics of proton release and the pH dependence significantly. Upon a flash excitation, three components “fast proton release,”“proton uptake” and “slow proton release” were observed at neutral pH in P77D. The p K a of PRC in the M intermediate was increased from 5.6 in the wild‐type to 7.0, and became closer to that in AR4, which is 8.4. The coupling strength between D85 and PRC were also weakened, as expected. These data indicate that the 77th residue in AR4 greatly account for the difference between the two proton pumps.