Abstract
Ab initio quantum chemical calculations have been performed to figure out a hypothetical structure that allows for reversible proton transport among Asp85, Schiff base, and Asp96 in bacteriorhodopsin. As an example of the hypothetical structure, we constructed a model system in which Asp85 and Asp96 are located in the Cs symmetry with respect to a vertical plane containing the N atom of the Schiff base and the O atom of the water molecule bound to the Schiff base. The proton transport reaction usually proceeds with the L→M→N in bacteriorhodopsin. In the present hypothetical structure, both of the proton transports (L→M→N and N→M→L) were revealed to occur reversibly.
