TABLE 2.
Initial rates of guanine nucleotide exchange reactions catalyzed by wild-type and mutant Dbs proteins on Cdc42, RhoA, and Rac1a
| Protein designation | Cdc42
|
RhoA
|
Rac1
|
Cdc42 (F56W)
|
||||
|---|---|---|---|---|---|---|---|---|
| (RF s−1) | Fold activation | (RF s−1) | Fold activation | (RF s−1) | Fold activation | (RF s−1) | Fold activation | |
| WT | 3.95 | 49 | 1.44 | 48 | 0.02 | 1 | 0.65 | 8 |
| L759M | 1.94 | 24 | 0.44 | 15 | 0.02 | 1 | ||
| L759I | 0.24 | 3 | 0.17 | 6 | 0.02 | 1 | ||
| L766M | 0.50 | 6 | 3.02 | 101 | 0.08 | 4 | ||
| L766I | 4.39 | 55 | 8.00 | 267 | 1.13 | 57 | 6.45 | 81 |
| Q752E | 2.05 | 26 | 1.62 | 54 | 0.02 | 1 | ||
| L759M/L766M | 0.25 | 3 | 1.35 | 45 | 0.05 | 3 | ||
| L759I/L766M | 0.07 | 1 | 0.38 | 13 | 0.02 | 1 | ||
| Q752E/L766M | 0.31 | 4 | 2.61 | 87 | 0.08 | 4 | ||
a
The initial rates of guanine nucleotide exchange for 2 μM wild-type (WT) GTPase stimulated by 0.1 μM concentrations of various Dbs proteins were determined by linear regression analysis of approximately the first 60 s of the Dbs-catalyzed reactions from Fig. 3. The fold activation for each Dbs protein reflects the ratio of the initial exchange rate measured for the GEF-containing reaction to the intrinsic rate of exchange for each GTPase. Intrinsic value of exchange: Cdc42, 0.08; RhoA, 0.03; Rac1, 0.02; and Cdc42 (F56W), 0.08 relative fluorescence (RF) units per second.