Exons 20 and 21 were deleted by homologous recombination. This sequence encodes the signature and Walker B motifs of the first ATP-binding domain, both critical for protein function. The splicing was predicted to cause a frame shift, creating a stop codon encoded by nucleotides 9-11 of exon 22. Western blot of mutant tissue lysates from brain, heart, lung and others confirmed deletion of the exons. (J:96865)