PT  - JOURNAL ARTICLE
AU  - Thiago Britto-Borges
AU  - Geoffrey J. Barton
TI  - A study of the structural properties of sites modified by the <em>O</em>-linked 6-N-acetylglucosamine transferase
AID  - 10.1101/115121
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 115121
4099  - http://biorxiv.org/content/early/2017/03/08/115121.short
4100  - http://biorxiv.org/content/early/2017/03/08/115121.full
AB  - Protein O-GlcNAcylation (O-GlcNAc) is an essential post-translational modification (PTM) in higher eukaryotes. The O-linked β-N-acetylglucosamine transferase (OGT), targets specific Serines and Threonines (S/T) in intracellular proteins. However, unlike phosphorylation, fewer than 25% of known O-GlcNAc sites match a clear sequence pattern. Accordingly, the three dimensional structures of O-GlcNAc sites were characterised to investigate the role of structure in molecular recognition. Of the 143/1,584 O-GlcNAc sites in 620 proteins were mapped to protein X-ray structures. The modified S/T were 1.7x more likely to be annotated in the REM465 field which defines missing residues in a protein structure, while 7 O-GlcNAc sites were solvent inaccessible and unlikely to be targeted by OGT. The 132/143 sites with complete backbone atoms clustered into 10 groups, but these were indistinguishable from clusters from unmodified S/T. This suggests there is no prevalent three-dimensional motif for OGT recognition. Predicted features from the 620 proteins were compared to unmodified S/T in O-GlcNAcylated proteins and globular proteins. The Jpred4 predicted secondary structure shows that modified S/T were more likely to be coils. 5/6 methods to predict intrinsic disorder indicated O-GlcNAcylated S/T to be significantly more disordered than unmodified S/T. Although the analysis did not find a pattern in the site three-dimensional structure, it revealed the residues around the modification site are likely to be disordered and suggests a potential role of secondary structure elements in OGT site recognition.