Ordered structure of the crystallized bovine 20S proteasome. 
Eukaryotic proteasomes are multicatalytic proteinase complexes with a molecular weight of 750 kDa, containing, respectively, two copies of a hetero-heptamer of alpha-type subunits and one of beta-type subunits, (alpha 1-7 beta 1-7)2.  Proteasome was purified from bovine liver and crystallized into a hexagonal system with cell dimensions of a = b = 121.83(2) A, c = 930.68(6) A. A cylindrical particle size of 122 A diameter and 155 A height was determined from the molecular packing in a unit cell.  The crystal gave diffraction spots up to at least 4.4 A resolution, which was the minimum spacing of the camera used.  The overall temperature factor of the enzyme was estimated to be in the range of 36.2 to 25.8 A2.  These results imply that the enzyme complex has a unique ordered structure comprising multisubunits with two types of hetero-heptamer.  This ordered structure may facilitate highly organized cooperation of individual functions of subunits within the enzyme complex.