A methionine to cysteine substitution at amino acid 527 (p.M527C) was introduced in exon 13 and a loxP-flanked neomycin resistance cassette was inserted downstream of exon 14. The neomycin resistance cassette was removed via cre-mediated recombination. This mutation has been shown to increase sensitivity to methanethiosulfonate reagents. (J:263973)