Purification and Characterization of the 20S Proteasome from Ostrich Skeletal Muscle

The proteasome is a high molecular weight, multisubunit and multicatalytic enzyme. Here we report the purification and characterization of ostrich skeletal muscle 20S proteasome. It was purified to homogeneity with Mr 700,000, pI 6.67 and a 'ladder' of 22.2-33.5 kDa bands on SDS-PAGE. The amino acid composition and amino-terminal sequences showed large identities to those of other species. For the three major activities, pH and temperature optima ranged between 8.0-11.0 and 40-70 degrees C, and stabilities between 5-12 and up to 40-60 degrees C. Substrate specificity and inhibitory effects were also studied. Many similarities to other sources were shown, with a few significant differences.