Figure 4.
Modulation of RGS GAP activity by PDEγ. Single turnover GTPase assays (see Methods) were performed in a mixture uwROS membranes containing 15 μM rhodopsin, 1 μM transducin, 1 μm GST-RGS domain, and the indicated concentrations of PDEγ. Δkinact is the difference between the GTP hydrolysis rate constant kinact in the presence and absence of GAP. Rate constants were determined by fitting the results with a single exponential function. (A) RGS9. (B) RGS11. (C) RGS6. (D) Time courses of GTP hydrolysis by Gtα in the absence of RGS (filled symbols) or with 1 μM RGS6 (open symbols, GST-RGS domain) in the presence of 0 (circles), 1 μM (triangles), or 2 μM (squares) PDEγ.