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Nat Commun. 2016 Jan 5;7:10175. doi: 10.1038/ncomms10175.

Structure of the polyisoprenyl-phosphate glycosyltransferase GtrB and insights into the mechanism of catalysis.

Author information

1
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032, USA.
2
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.
3
Department of Pharmacology and Physiology, George Washington University, Washington, District of Columbia 20037, USA.
4
Department of Integrative Systems Biology, George Washington University, Washington, District of Columbia 20037, USA.
5
NE-CAT and Department of Chemistry and Chemical Biology, Cornell University, Argonne National Laboratory, Argonne, Illinois 60439, USA.
6
New York Structural Biology Center, X4 Beamlines, Brookhaven National Laboratory, Upton, New York 11973, USA.
7
Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA.
8
New York Consortium on Membrane Protein Structure, New York Structural Biology Center, New York, New York 10027, USA.
9
Department of Informatics, Bioinformatics and Computational Biology, Garching 85748, Germany.
10
Institute for Advanced Study (TUM-IAS), TUM (Technische Universität München), Garching 85748, Germany.

Abstract

The attachment of a sugar to a hydrophobic polyisoprenyl carrier is the first step for all extracellular glycosylation processes. The enzymes that perform these reactions, polyisoprenyl-glycosyltransferases (PI-GTs) include dolichol phosphate mannose synthase (DPMS), which generates the mannose donor for glycosylation in the endoplasmic reticulum. Here we report the 3.0 Å resolution crystal structure of GtrB, a glucose-specific PI-GT from Synechocystis, showing a tetramer in which each protomer contributes two helices to a membrane-spanning bundle. The active site is 15 Å from the membrane, raising the question of how water-soluble and membrane-embedded substrates are brought into apposition for catalysis. A conserved juxtamembrane domain harbours disease mutations, which compromised activity in GtrB in vitro and in human DPM1 tested in zebrafish. We hypothesize a role of this domain in shielding the polyisoprenyl-phosphate for transport to the active site. Our results reveal the basis of PI-GT function, and provide a potential molecular explanation for DPM1-related disease.

PMID:
26729507
PMCID:
PMC4728340
DOI:
10.1038/ncomms10175
[Indexed for MEDLINE]
Free PMC Article

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