Figure 5.

GCAP1 and GCAP2 compete for the activation of RetGC1. The native RetGC1 activity in Gcaps^−/− RetGC2^−/− mouse retinas was assayed as described under “Experimental procedures” in the absence of GCAPs (▴) or in the presence of 3 μm mouse GCAP1 (red circles) or 0.5 μm GCAP2 (black circles). Variable concentrations of the competing bovine M26R GCAP1 were added to the assay as indicated. The data, average ± S.D. (error bars) of two to four independent measurements, were fitted assuming a sigmoidal Hill function.