The targeting vector is designed to insert a E to A point mutation into the catalytic domain (exon 11) by site-directed mutagenesis. An FRT-flanked neomycin cassette is inserted downstream of exon 11. The mutation results in a A to C change at nucleotide 6829 altering the corresponding amino acid from glutamate to alanine. Flp-mediated recombination removed the FRT-flanked neo cassette. (J:217858)