Figure 2.

Bicarbonate- and nickel-dependent activation of urease apoprotein in the UreD-UreF-UreG-apourease complex. (A) Samples of UreD-UreF-UreG-apourease complex (0.2 μM) were incubated at 37°C in standard activation buffer containing 100 μM NiCl₂ and 0.1 (○), 0.5 (▾), 5 (▴), 25 (⧫), 75 (■), or 100 (●) mM NaHCO₃. (B) Similar incubations used standard activation buffer containing 100 mM NaHCO₃ and 20 (▾), 50 (▴), 100 (●), 200 (■), or 400 (◊) μM NiCl₂. For both sets of studies, aliquots were removed at the indicated times and the samples were assayed for urease activity.