Exon 3 was replaced with a modified exon 3 in which nucleotide substitutions replaces a methionine with glycine at position 129 (M129G). This mutation is expected to disrupt the gatekeeper residue in the ATP-binding pocket possibly rendering the protein susceptible to small molecular analogues of the general kinase inhibitor PP1. Cre-mediated recombination removed the floxed neo cassette inserted downstream of exon 2. Activity assay confirmed the sensitivity to 1NMPP1 inhibition.