TCB Publications - Abstract

TCB Publications - Abstract

William Humphrey, Ernst Bamberg, and Klaus Schulten. Photoproducts of bacteriorhodopsin mutants: A molecular dynamics study. Biophysical Journal, 72:1347-1356, 1997. (PMC: 1184517)

HUMP97 Molecular dynamics simulations of wild-type bacteriorhodopsin (bR) and of its D85N, D85T, D212N, and Y57F mutants have been carried out to investigate 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 $N{-}H^{+}$ oriented toward Asp-85 and hydrogen- bonded to a water molecule; 3) 13,14-dicis 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.

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