Figure 1.

Ca²⁺-bound neurocalcin δ stimulates ANF-RGC activity. COS cells were transfected with ANF-RGC cDNA and their membrane fraction was analyzed for neurocalcin δ-dependent cyclase activity in the absence (open circles) and presence of 10 μM Ca²⁺ (closed circles). COS cells transfected with an empty vector were analyzed identically (closed diamonds). The extracellular hormone ligand of ANF-RGC, the atrial natriuretic factor (ANF) was absent from the reaction mixture. The experiment was done in triplicate and repeated four times. The results shown are average ± SD from these experiments. The EC₅₀ value was determined graphically. Neurocalcin δ used was myristoylated. The myristoylated form of neurocalcin δ was expressed and purified as described in Krishnan et al. (2004).