Abstract
Bacteriorhodopsin (bR) is a membrane protein, which absorbs light by its retinal chromophore. The absorbed light energy is used to pump protons from the cytoplasm into the extra-cellular space. To understand the mechanism of the proton pumping, the determination of high resolution structure for bR including ordered water molecules will be required. The atomic model of bR was first built by a pioneer work by Henderson's group on electron crystallography at 3.5 Å resolution, and recently some models analyzed by both X-ray and electron crystallography at higher resolution were reported. Here we describe the structure of bR at 3.0 Å resolution determined by electron crystallography by our group and compare it with the atomic model analyzed by X-ray crystallography at 2.3 Å resolution. In addition, we will discuss the possibility of visualization of charge status by electron crystallography using the characteristic feature of atomic scattering factors for electron.
