Relative activity of variant Wzb proteins. Endpoint reactions at 75°C (black bars) and kinetic reactions at 47°C (gray bars) were carried out in 50 mM MES, 50 mM HEPES buffer containing 1% BSA in the presence of Cu2+, Co2+, Fe3+ (at 0.1 mM each) and Mn2+, Mg2+ (at 0.5 mM each). In the case of endpoint reactions, a 30-min pre-incubation at 75°C was carried out before adding 2.5 mM p NPP. Reactions were stopped after 10 min. incubation by the addition of 100 mM (final conc.) sodium vanadate.