The gene was targeted with a construct containing a FRT-flanked neomycin resistance cassette and a point mutation that changes the triplet encoding lysine at amino acid position 1973 of the protein to a methionine codon (K1973M). Germline expression of enhanced FLP recombinase resulted in deletion of neomycin resistance cassette, leaving a single FRT site and the point mutation. The protein product lacks kinase activity in the absence of phosphorylation. (J:211844)