Structural basis for mammalian nucleotide sugar transport

Abstract
Data availability
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Abstract

Nucleotide-sugar transporters (NSTs) are critical components of the cellular glycosylation machinery. They transport nucleotide-sugar conjugates into the Golgi lumen, where they are used for the glycosylation of proteins and lipids, and they then subsequently transport the nucleotide monophosphate byproduct back to the cytoplasm. Dysregulation of human NSTs causes several debilitating diseases, and NSTs are virulence factors for many pathogens. Here we present the first crystal structures of a mammalian NST, the mouse CMP-sialic acid transporter (mCST), in complex with its physiological substrates CMP and CMP-sialic acid. Detailed visualization of extensive protein-substrate interactions explains the mechanisms governing substrate selectivity. Further structural analysis of mCST's unique lumen-facing partially-occluded conformation, coupled with the characterization of substrate-induced quenching of mCST's intrinsic tryptophan fluorescence, reveals the concerted conformational transitions that occur during substrate transport. These results provide a framework for understanding the effects of disease-causing mutations and the mechanisms of this diverse family of transporters.

Data availability

Atomic coordinates and structure factors have been deposited in the Protein Data Bank (PDB) with entries 6OH2, 6OH3, and 6OH4.

The following data sets were generated

1. Ahuja S
2. Whorton MR
(2019) X-ray crystal structure of the mouse CMP-sialic acid transporter in complex with CMP, by lipidic cubic phase
Protein Data Bank, 6OH2.

https://www.rcsb.org/structure/6OH2
1. Ahuja S
2. Whorton MR
(2019) X-ray crystal structure of the mouse CMP-sialic acid transporter in complex with CMP- sialic acid, by lipidic cubic phase
Protein Data Bank, 6OH3.

https://www.rcsb.org/structure/6OH3
1. Ahuja S
2. Whorton MR
(2019) X-ray crystal structure of the mouse CMP-sialic acid transporter in complex with CMP, by hanging drop vapor diffusion
Protein Data Bank, 6OH4.

https://www.rcsb.org/structure/6OH4

Article and author information

Author details

Shivani Ahuja

Vollum Institute, Oregon Health and Science University, Portland, United States

Competing interests
The authors declare that no competing interests exist.
Matthew R Whorton

Vollum Institute, Oregon Health and Science University, Portland, United States

For correspondence
whorton@ohsu.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-9915-7467

Funding

Oregon Health and Science University

Shivani Ahuja
Matthew R Whorton

National Institutes of Health (R01GM130909)

Shivani Ahuja
Matthew R Whorton

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Copyright

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.