TABLE 2.
Protein or proteasome | Preincubation temp (°C)a | Activityb |
---|---|---|
α | 0, 37, 65, 85 | UDc |
β(Δpro) | 0, 37, 65, 85 | UD |
α-β(Δpro)d | 0 | UD |
α-β(Δpro) | 37 | 31.3 ± 1.55 |
α-β(Δpro) | 65 | 48.2 ± 0.74 |
α-β(Δpro) | 85 | 47.7 ± 3.01 |
700-kDa proteasomes | 0 | 106 ± 2.2 |
∼1.5-MDa proteasomes | 0 | 137 ± 8.6 |
Proteins (0.75 mg of protein per ml of Tris buffer) were preincubated at the indicated temperatures for 15 min.
Activity measured in micromoles per minute per milligram of protein. Hydrolysis of Suc-LLVY-Amc was measured at 37°C using 20 μM substrate and 0.06 mg of purified protein in 1 ml of Tris buffer with 6% (vol/vol) dimethyl sulfoxide.
UD, undetectable.
α-β(Δpro), equimolar ratios of the separately purified α and β(Δpro) proteins mixed prior to preincubation.