Sequence for a Gly-Ser-Gly spacer, a OneSTrEPtag (OST), two STOP codons, a loxP site, the mouse Ace (angiotensin I converting enzyme (peptidyl-dipeptidase A) 1) promoter, the cre recombinase gene, a neomycin resistance gene cassette, and a second loxP site, was inserted in-frame after sequence coding for at the 3 end of the gene coding sequence in exon 11. Cre-mediated self-excision removed the cre+neo cassette in the male germline. The fusion of the OST to the protein can be used in affinity purification. Protein reduction from this allele is reduced to 25% of wild-type gene expression. (J:209882)