FIG. 2.

Effect of temperature on β-casein degradation by archaeal 20S proteasomes. Hydrolysis of bovine β-casein was measured at the temperatures indicated using 0.2 mg of substrate protein and 0.05 mg of purified 20S proteasome in 1 ml of 20 mM Tris–1 mM DTT (pH 7.2). Abbreviations: Mj20S, Ta20S, and Mt20S, M. jannaschii, T. acidophilum, and M. thermophila 20S proteasomes, respectively; grps, groups.