ELECTRON CRYOMICROSCOPY OF 2-DIMENSIONAL CRYSTALS OF THE H-ATPASE FROM CHLOROPLASTS()

The H+-ATPase from spinach chloroplasts was isolated and purified, Two -dimensional crystals were obtained from the protein/lipid/detergent m icelles by treatment with phospholipase and simultaneous removal of de tergent and fatty acids by Biobeads. The resulting two-dimensionally o rdered arrays were investigated by electron cryomicroscopy, The ordere d arrays showed top view projections of CF0F1. The images were analyse d by correlation averaging, In this view CF0F1 has dimensions of 11.4 x 9 am. The average view shows a strongly asymmetric molecule, in cont rast to the rather hexagonal features of CF1, previously analyzed from two-dimensional arrays. It is concluded that this is due either to an asymmetric structure and positioning of CP0 relative to CF1 or to a r earrangement of CF1 subunits induced by binding of CF0 to CP1.