FIG. 7.

Thermal stability of the recombinant form of NoxA2. rNoxA2 was incubated at 83°C in 50 mM NaPi (pH 7.6, as determined at 55°C) (open circles) or 50 mM Tris (pH 7.8, as determined at 55°C) (solid circles). Aliquots of rNoxA2 (0.5 μg) were removed and monitored at 340 nm for NADH oxidation in 50 mM NaPi (pH 7.6), 0.2% CHAPS, 20 μM FAD, and 100 μM NADH at 55°C. Half-life of rNox following incubation in buffer was estimated to be 40 min in NaPi and 12 min in Tris. (Inset) NoxA2 (phenyl-Sepharose fraction) from A. fulgidus was incubated at 83°C in NaPi prior to assaying as explained above. One unit equals 1 μg of total protein; the half-life of NoxA2 averaged 35 h.