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Photoproducts of Bacteriorhodopsin Mutants: A Molecular Dynamics Study

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Bamberg,  Ernst
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Citation

Humphrey, W. F., Bamberg, E., & Schulten, K. (1997). Photoproducts of Bacteriorhodopsin Mutants: A Molecular Dynamics Study. Biophysical Journal, 72(3), 1347-1356. doi:10.1016/S0006-3495(97)78781-2.


Cite as: http://hdl.handle.net/21.11116/0000-0007-6498-D
Abstract
Molecular dynamics simulations of wild-type bacteriorhodopsin (bR) and of its D85N, D85T, D212N, and Y57F mutants have been carried out to investigate possible differences in the photoproducts of these proteins. For each mutant, a series of 50 molecular dynamics simulations of the photoisomerization and subsequent relaxation process were completed. The photoproducts can be classified into four distinct classes: 1) 13-cis retinal, with the retinal N-H+ bond oriented toward Asp-96; 2) 13-cis retinal, with the N-H+ oriented toward Asp-85 and hydrogen-bonded to a water molecule; 3) 13,14-di-cis retinal; 4) all-trans retinal. Simulations of wild-type bR and of its Y57F mutant resulted mainly in class 1 and class 2 products; simulations of D85N, D85T, and D212N mutants resulted almost entirely in class 1 products. The results support the suggestion that only class 2 products initiate a functional pump cycle. The formation of class 1 products for the D85N, D85T, and D212N mutants can explain the reversal of proton pumping under illumination by blue and yellow light.