Figure 1.

Guanylyl cyclase activity of the sGC-GFP fusion protein. A plasmid encoding GFP fused to the C-terminus of sGC was introduced in gca^-/sgc^- null cells to obtain the sGC-GFP^oe strain. (A) Guanylyl cyclase activity in vitro; gca^-/sgc^-, sGC-GFP^oe, and wild-type AX3 cells were lysed, and Mn²⁺-dependent activity was measured in the lysates. The mean activity and SD are shown of two independent experiments, each with lysis in triplicate. (B) cGMP formation in vivo; 5-h–starved cells were stimulated with 100 nM cAMP. At the indicated time points, the cells were lysed and the amount of accumulated cGMP was determined. The data shown are the means of three experiments.