Three-dimensional protein structures bring us a deeper insight into the biological function. The main aim of my group is the X-ray structure determination of the biological macromolecular assemblies including membrane protein complexes in order to elucidate the molecular mechanism of the highly organized biological processes at atomic level. Here, I report two examples; One is structural studies of photosynthetic membrane protein complex and related redox enzymes, and the other is crystal structure analyses of dynein motor.