Nucleotide substitutions replaced the threonine and serines in the TxxSS motif in the last 12 amino acids of the sequence with alanines (p.T371A and p.(S374_S375delinsAA)). A floxP site flanked neomycin resistance gene cassette was inserted into the 3' UTR. Subsequent cre-mediated recombination removed the neo cassette. (J:176118)