FIG. 4.

Purification and ATPase assays. (A) Proteins were purified as described in the text, about 1 μg of the purified proteins was separated on a 10% Laemmli SDS-polyacrylamide gel, and then the gel was stained with Coomassie blue. (B) Initial reaction rates as a percentage of the wild-type ATPase activity of the different mutants in the presence of 1 mM ATP and 300 ng/μl of total yeast RNA. Velocities were normalized for the same protein concentration (1 nM). (C) Initial reaction velocities of the intragenic suppressors of the F405L mutation and of the suppressors in isolation. M, molecular size marker, in kilodaltons; WT, wild type.