FIGURE 8.

Isomerase activity of I272A and L343A mutants in PDI and abb′x backgrounds. Reactivation of denatured and reduced RNase A (8 μm) in glutathione redox buffer at 25 °C was determined by monitoring the absorbance increase at 296 nm due to hydrolysis of 4.5 mm cCMP in the absence (♦) or presence of 3 μm PDI (■), I272A PDI (○), L343A PDI (▵), abb′x (□), I272A abb′x (●), and L343A abb′x (▴) (A). The slope of the initial linear increase in RNase activity after the lag time (in A) was taken as the isomerase activity, and the enzyme activities of the background proteins (PDI and abb′x) were taken as 100%. Data are expressed as mean ± S.D. (n = 3) (B).