Figure 4.

GCAP1 titrations of RetGC1 activity with wild-type GCAP1 (blackened circles), E155G mutant (blackened triangles) and an equimolar mixture of wild-type and E155G mutant (open squares). Curves were fitted to the data points on the basis of the relation v=[GCAP1]V_max/(K_m^app[GCAP1]+[GCAP1]), where K_m ^app[GCAP1] is the GCAP1 concentration required for half maximal activation and where V_max is the maximum specific activation. Values of V_max and K_m ^app[GCAP1] are derived from the fitted curves are given in table 1.