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1 November 2006 Water as a Cofactor in the Unidirectional Light-Driven Proton Transfer Steps in Bacteriorhodopsin
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Abstract

Recent evidence for involvement of internal water molecules in the mechanism of bacteriorhodopsin is reviewed. Water O–H stretching vibration bands in the Fourier transform IR difference spectra of the L, M and N intermediates of bacteriorhodopsin were analyzed by photoreactions at cryogenic temperatures. A broad vibrational band in L was shown to be due to formation of a structure of water molecules connecting the Schiff base to the Thr46-Asp96 region. This structure disappears in the M intermediate, suggesting that it is involved in transient stabilization of the L intermediate prior to proton transfer from the Schiff base to Asp85. The interaction of the Schiff base with a water molecule is restored in the N intermediate. We propose that water is a critical mobile component of bacteriorhodopsin, forming organized structures in the transient intermediates during the photocycle and, to a large extent, determining the chemical behavior of these transient states.

Akio Maeda, Joel E. Morgan, Robert B. Gennis, and Thomas G. Ebrey "Water as a Cofactor in the Unidirectional Light-Driven Proton Transfer Steps in Bacteriorhodopsin," Photochemistry and Photobiology 82(6), 1398-1405, (1 November 2006). https://doi.org/10.1562/2006-01-16-IR-779
Received: 16 January 2006; Accepted: 1 April 2006; Published: 1 November 2006
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