Cryo-EM structure provides insights into the dimer arrangement of the O-linked β-N-acetylglucosamine transferase OGT

Abstract

The O-linked β-N-acetylglucosamine modification is a core signalling mechanism, with erroneous patterns leading to cancer and neurodegeneration. Although thousands of proteins are subject to this modification, only a single essential glycosyltransferase catalyses its installation, the O-GlcNAc transferase, OGT. Previous studies have provided truncated structures of OGT through X-ray crystallography, but the full-length protein has never been observed. Here, we report a 5.3 Å cryo-EM model of OGT. We show OGT is a dimer, providing a structural basis for how some X-linked intellectual disability mutations at the interface may contribute to disease. We observe that the catalytic section of OGT abuts a 13.5 tetratricopeptide repeat unit region and find the relative positioning of these sections deviate from the previously proposed, X-ray crystallography-based model. We also note that OGT exhibits considerable heterogeneity in tetratricopeptide repeat units N-terminal to the dimer interface with repercussions for how OGT binds protein ligands and partners.

Metadata

Authors/Creators:

Meek, Richard W. (rwm512@york.ac.uk)
Blaza, James N. https://orcid.org/0000-0001-5420-2116
Busmann, Jil A.
Alteen, Matthew G.
Vocadlo, David J.
Davies, Gideon J. https://orcid.org/0000-0002-7343-776X

Funding Information: G.J.D. thanks the Royal Society for the Ken Murray Research Professorship and R.W.M. for the associated PDRA funding (RP\EA\180016). J.N.B. is supported by a UKRI Future Leader Fellowship (MR/T040742/1). D.J.V. is supported by a Tier I Canada Research Chair in Chemical Glycobiology and an E.W.R. Steacie Memorial Fellowship. This research and J.A.B and M.A.A were supported by the Canadian Institutes of Health Research (CIHR; PJT-148732, PJT-156202) and from the Networks of Centres of Excellence GlycoNet (Team Grant CD-1). The authors also thank the Centre for High-Throughput Chemical Biology (HTCB) for access to core facilities. We acknowledge Diamond Light Source for access and support of the cryo-EM facilities at the UK’s national Electron Bio-imaging Centre (eBIC) [under proposal EM 19832-26], funded by the Wellcome Trust, MRC and BBRSC. We also thank Sarah Neumann for help operating the microscope. This project was undertaken on the Viking Cluster, which is a high-performance compute facility provided by the University of York. We are grateful for computational support from the University of York High Performance Computing service, Viking and the Research Computing team. We wish to acknowledge the work of Dr Andrew Leech at the University of York Bioscience Technology Facillity for assistance with SEC-MALLS, Dr Johan Turkenburg and Sam Hart for coordinating data collection, Dr Svet Tzokov for his help in acquiring preliminary data, Dr Sarah Neumann for operating the microscope at eBIC, Dr Huw Jenkins and De-Sheng Ker for data processing assistance, and the YSBL technicians for technical support. Publisher Copyright: © 2021, The Author(s).

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