A floxed construct containing a Npr2 cDNA encoding exons 8- 22, and IRES site, eGFP gene, and FRT flanked pgk-neo casstte was inserted in intron 7 and point mutations in the seven serine and threonine sites in exons 8 and 9 were introduced via homologous recombination. The point mutations converted the serine and threonine codons to glutamate codons. Cre-mediated recombination removed the entire construct. The resulting protein behaves as if it is constitutively phosphorylated. (J:228790)