Received March 20, 2001; Revision received May 9, 2001
In the last few years, detailed structural information from high-resolution x-ray diffraction has been added to the already large body of spectroscopic and mutational data on the bacteriorhodopsin proton transport cycle. Although there are still many gaps, it is now possible to reconstruct the main events in the translocation of the proton and how they are coupled to the photoisomerization of the retinal chromophore. Future structural work will concentrate on describing the details of the individual proton transfer steps during the photocycle.
KEY WORDS: bacteriorhodopsin, x-ray diffraction, proton transport cycle, retinal