Exon 2 was replaced with a modified exon 2 in which nucleotide substitutions (TCA to GAG) result in the amino acid susbtitution of glutamic acid for serine at position 26 (S26E). This mutation mimics phosphorylation at this site. Cre-mediated recombination removed the floxed neomycin resistance cassette inserted downstream of the modified exon 2. (J:200716)