Fig. 6: Working model of substrate recognition and modification by human OGT.
From: Cryo-EM structure of human O-GlcNAcylation enzyme pair OGT-OGA complex

For clarity, only one OGT monomer (colored in blue) is shown. OGT binds to the intrinsically disordered regions (IDRs) (colored in yellow) of OGA-like substrates through its TPR domain. The superhelical turns of the TPR domain have to partially unwind to allow the IDR to access its lumen. The superhelical turns then reform and wrap around the IDR in a topological embrace, which lengthens the lifetime of the OGT-substrate complex for optimal O-GlcNAcylation. TPR tetratricopeptide repeat, GTD glycosyltransferase domain, IDR intrinsically disordered region.