ABSTRACT
The photosynthetic membrane of Rhodopseudomonas viridis, a purple nonsulfur photosynthetic bacterium, has emerged as a major system for the study of biological membranes and their polypeptides. Rather, the fact that these membranes and their components can be induced to form well-ordered two- and three-dimensional crystalline lattices has made them exceptionally useful as objects of crystallographic study. The highly ordered nature of the two-dimensional crystalline sheets also allowed us to carry out a determination of the three-dimensional structure of the reaction center proteins within the sheets. The reconstructed three-dimensional data have been sampled by drawing contours at fixed intervals in order to build up a three-dimensional map of the structure. Michel's three-dimensional crystals of the Rhodopseudomonas viridis reaction center3 have enabled a three-dimensional map to be produced at the atomic level of resolution, and have yielded interesting information concerning the organization of prosthetic groups in the central region of the reaction center.
