FIGURE 3.

Characterization of HspB. A, pH dependence of HspB stability. The enzyme was incubated overnight in buffers of various pH at 25 °C. B, thermostability of HspB. The enzyme was incubated in Tris-HCl buffer (50 mm, pH 8.0) at varying temperatures for 30 min. C, effects of metal salts on HspB stability. CK, without metal salt; Na, Na⁺; Ni, Ni²⁺; Co, Co²⁺; Ca, Ca²⁺; Cu, Cu²⁺; Mn, Mn²⁺; Zn, Zn²⁺; Mg, Mg²⁺; K, K⁺; Mo, MoO₄²⁻; W, WO₄²⁻. D, oxygen consumption of the HspB reaction. ▲, ●, and ■ indicate the oxygen declines from different initial concentrations. For the above four experiments, enzyme activity was determined according to the standard assay at 25 °C and pH 8.0.