Ion pumps are important in maintaining cellular integrity.
However, the molecular mechanisms of these pumps are not understood. This relatively small and simple protein provides a convenient system for elucidating the mechanism of an active transport system. However, the pre-discharge state is much more difficult to study. This mutant also pumps protons but has a simpler photocycle, making it even an more promising candidate for the characterization of the pumping mechanism. The figure below shows the helices of bR, emphasizing the retinal binding pocket, which undergoes structural changes during the course of the photocycle.