Aspartate residues far from the active site drive O-GlcNAc transferase substrate selection

Here we use protein microarray technology and proteome-wide glycosylation profiling to show that conserved aspartate residues in the tetratricopeptide repeat (TPR) lumen of OGT drive substrate selection. Changing these residues to alanines alters substrate selectivity and unexpectedly increases rates of protein glycosylation. Our findings support a model where sites of glycosylation for many OGT substrates are determined by TPR domain contacts to substrate side chains five to fifteen residues Cterminal to the glycosite. In addition to guiding design of inhibitors that target OGT’s TPR domain, this information will inform efforts to engineer substrates to explore biological functions.