Bacteriorhodopsin, Chemistry of

Abstract

Thirty years of research with bacteriorhodopsin has provided answers to many questions about how protons are transported by transmembrane pumps. In this small seven‐transmembrane protein, absorption of light by the retinal chromophore initiates a reaction cycle in which the initial state recovers through multiple conformational changes of the retinal and the protein, and a proton is translocated stepwise from one side of the membrane to the other. Spectroscopy, extensive use of site‐specific mutations, and crystallography have defined the photocycle reactions in atomic detail and provide a step‐by‐step description of the proton transfers, the transient local and global perturbations in the protein and how they arise, and the energy flow through the system, which add up to the mechanism of the pump.