Table 1

Concentration-dependence of RGS effects on steady-state GTPase activity. Carbachol-dependent GTPase activity was measured at multiple concentrations of RGS2 and RGS4 at free magnesium concentrations of 0.5 and 7.5 mM, as shown in Fig. 5. Data from individual dose-response curves for RGS2 and for RGS4 at 7.5 mM free magnesium were fitted to the Hill equation. RGS4 in the presence of 0.5 mM free magnesium yielded bell-shaped curves, which were individually analyzed as the sum of two rectangular hyperbolae. The parameters presented are mean values ± S.D.

[Mg2+]freeEC50nHKupKdownn
mM μM μM μM
RGS20.51.3  ±  0.62.6  ±  0.55
RGS27.52.2  ±  1.23.5  ±  0.64
RGS40.50.14  ±  0.084.0  ±  3.06
RGS47.50.49  ±  0.071.8  ±  0.65