Threonine codon 125 (ACG) was changed to alanine (GCG) (p.T125A) and serine codon 127 (TCG) to alanine (GCG) (p.S127A) using an sgRNA and an ssODN template with CRISPR/Cas9 technology. These mutations of the highly conserved residues in the helix 1 domain prevent phosphorylation of the residues. (J:327336)