Abstract

Core-fucosylation is an essential biological modification by which a fucose is transferred from GDP-β-L-fucose to the innermost N-acetylglucosamine residue of N-linked glycans. A single human enzyme α1,6-fucosyltransferase (FUT8) is the only enzyme responsible for this modification via the addition of an α-1,6-linked fucose to N-glycans. To date, the details of substrate recognition and catalysis by FUT8 remain unknown. Here, we report the crystal structure of FUT8 complexed with GDP and a biantennary complex N-glycan (G0), which provides insight into both substrate recognition and catalysis. FUT8 follows an SN2 mechanism and deploys a series of loops and an α-helix which all contribute in forming the binding site. An exosite, formed by one of these loops and an SH3 domain, is responsible for the recognition of branched sugars, making contacts specifically to the α1,3 arm GlcNAc, a feature required for catalysis. This information serves as a framework for inhibitor design, and helps to assess its potential as a therapeutic target.

Highlights

  • GDP-β-L-fucose to the innermost N-acetylglucosamine residue of N-linked glycans

  • Gene knockout of FUT8 in mice led to early postnatal death, severe growth retardation and emphysema-like changes in the lung, and revealed that this modification is crucial for the activation of growth factor receptors[1,3]

  • FUT8 is upregulated in numerous types of cancer, suggesting that blocking its activity could be a promising strategy for improving antitumor immune responses[9]

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Summary

Introduction

GDP-β-L-fucose to the innermost N-acetylglucosamine residue of N-linked glycans. A single human enzyme α1,6-fucosyltransferase (FUT8) is the only enzyme responsible for this modification via the addition of an α-1,6-linked fucose to N-glycans. An exosite, formed by one of these loops and an SH3 domain, is responsible for the recognition of branched sugars, making contacts to the α1,3 arm GlcNAc, a feature required for catalysis. This information serves as a framework for inhibitor design, and helps to assess its potential as a therapeutic target. The acceptor specificity of FUT8 requires the presence of a terminal GlcNAc moiety on the α1,3 arm of the N-glycan but shows a higher degree of flexibility on the α1,6 arm[10] This substrate preference does not necessarily demand the presence of a peptide/protein[10]. In these cases a peptide/protein moiety attached to the first GlcNAc via an N-glycosidic linkage[11] is necessary

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