Two-dimensional rhodopsin crystals from disk membranes of frog retinal rod outer segments

Two-dimensional crystals of rhodopsin have been prepared from purified frog disk membranes by using the detergent Tween 80. The space group of the orthorhombic crystals is p22121; the unit cell dimensions are 47 X 151 A. Projection maps of negatively stained preparations have been calculated to a resolution of approximately 22 A. The rhodopsin molecules are associated as dimers that appear to be slightly sigmoidal and are 20-25 A in width and 70-80 A in length.