Structure of protein O-mannose kinase reveals a unique active site architecture
- School of Life Sciences, Peking University, China
- Howard Hughes Medical Institute, University of Iowa Roy J. and Lucille A. Carver College of Medicine, United States
- National Institute of Biological Sciences, China
- University of Texas Southwestern Medical Center, United States
- Peking University, China
- University of Iowa, United States
- University of California, San Diego, United States
Abstract
The 'pseudokinase' SgK196 is a protein O-mannose kinase (POMK) that catalyzes an essential phosphorylation step during biosynthesis of the laminin-binding glycan on α-dystroglycan. However, the catalytic mechanism underlying this activity remains elusive. Here we present the crystal structure of Danio rerio POMK in complex with Mg2+ ions, ADP, aluminum fluoride, and the GalNAc-β3-GlcNAc-β4-Man trisaccharide substrate, thereby providing a snapshot of the catalytic transition state of this unusual kinase. The active site of POMK is established by residues located in non-canonical positions and is stabilized by a disulfide bridge. GalNAc-β3-GlcNAc-β4-Man is recognized by a surface groove, and the GalNAc-β3-GlcNAc moiety mediates the majority of interactions with POMK. Expression of various POMK mutants in POMK knockout cells further validated the functional requirements of critical residues. Our results provide important insights into the ability of POMK to function specifically as a glycan kinase, and highlight the structural diversity of the human kinome.
Article and author information
Author details
Funding
National Natural Science Foundation of China (31570735)
- Junyu Xiao
National Key Research & Development Plan of China (2016YFC0906000)
- Junyu Xiao
National Institute of Diabetes and Digestive and Kidney Diseases (DK18849, DK18024)
- Jack E Dixon
Paul D. Wellstone Muscular Dystrophy Cooperative Research Center (1U54NS053672)
- Kevin P Campbell
Howard Hughes Medical Institute
- Jack E Dixon
- Kevin P Campbell
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2016, Zhu et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Structure of protein O-mannose kinase reveals a unique active site architecture
eLife 5:e22238.
https://doi.org/10.7554/eLife.22238
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