3D structural analysis of protein O-mannosyl kinase, POMK, a causative gene product of dystroglycanopathy.

Abstract

Orchestration of the multiple enzymes engaged in O-mannose glycan synthesis provides a matriglycan on α-dystroglycan (α-DG) which attracts extracellular matrix (ECM) proteins such as laminin. Aberrant O-mannosylation of α-DG leads to severe congenital muscular dystrophies due to detachment of ECM proteins from the basal membrane. Phosphorylation at C6-position of O-mannose catalyzed by protein O-mannosyl kinase (POMK) is a crucial step in the biosynthetic pathway of O-mannose glycan. Several mis-sense mutations of the POMK catalytic domain are known to cause a severe congenital muscular dystrophy, Walker-Warburg syndrome. Due to the low sequence similarity with other typical kinases, structure-activity relationships of this enzyme remain unclear. Here, we report the crystal structures of the POMK catalytic domain in the absence and presence of an ATP analogue and O-mannosylated glycopeptide. The POMK catalytic domain shows a typical protein kinase fold consisting of N- and C-lobes. Mannose residue binds to POMK mainly via the hydroxyl group at C2-position, differentiating from other monosaccharide residues. Intriguingly, the two amino acid residues K92 and D228, interacting with the triphosphate group of ATP, are donated from atypical positions in the primary structure. Mutations in this protein causing muscular dystrophies can now be rationalized.

• Authors: Masamichi Nagae, Sushil K Mishra, Makiko Neyazaki, Rika Oi, Akemi Ikeda, Naohiro Matsugaki, Satoko Akashi, Hiroshi Manya, Mamoru Mizuno, Hirokazu Yagi, Koichi Kato, Toshiya Senda, Tamao Endo, Terukazu Nogi, Yoshiki Yamaguchi
• Journal: Genes to cells : devoted to molecular & cellular mechanisms (Genes Cells) Vol. 22 Issue 4 Pg. 348-359 (Apr 2017) ISSN: 1365-2443 [Electronic] England
• PMID: 28251761 (Publication Type: Journal Article)
• Copyright: © 2017 The Authors Genes to Cells published by Molecular Biology Society of Japan and John Wiley & Sons Australia, Ltd.

Chemical References

• Dystroglycans
• POMK protein, human
• POMK protein, mouse
• Protein Kinases

Topics

• Animals
• Catalytic Domain
• Crystallography, X-Ray
• Dystroglycans (chemistry)
• Humans
• Mice
• Muscular Dystrophies (genetics, metabolism)
• Mutation
• Protein Kinases (chemistry, genetics, metabolism)