FIGURE 4.

The N-terminal 22 amino acids of hAha1 are dispensable for stimulating Hsp90's ATPase activity. The ATPase activity of hHsp90 (dark gray) and yHsp90 (light gray) was measured with and without hAha1, Δ22hAha1 or yAha1 using a coupled enzymatic system described in “Experimental Procedures.” The N-terminal 22 amino acids of hAha1 that are necessary for prevention of rhodanese aggregation are dispensable for hHsp90 ATPase stimulation. All measurements were performed in triplicate, and standard deviation is indicated by error bars.