Structures of DPAGT1 Explain Glycosylation Disease Mechanisms and Advance TB Antibiotic Design

Summary

Protein N-glycosylation is a widespread post-translational modification. The first committed step in this process is catalysed by dolichyl-phosphate N-acetylglucosamine-phosphotransferase DPAGT1 (GPT/E.C. 2.7.8.15). Missense DPAGT1 variants cause congenital myasthenic syndrome and disorders of glycosylation. In addition, naturally-occurring bactericidal nucleoside analogues such as tunicamycin are toxic to eukaryotes due to DPAGT1 inhibition, preventing their clinical use. Our structures of DPAGT1 with the substrate UDP-GlcNAc and tunicamycin reveal substrate binding modes, suggest a mechanism of catalysis, provide an understanding of how mutations modulate activity (thus causing disease) and allow design of non-toxic “lipid-altered” tunicamycins. The structure-tuned activity of these analogues against several bacterial targets allowed the design of potent antibiotics for Mycobacterium tuberculosis, enabling treatment in vitro, in cellulo and in vivo, providing a promising new class of antimicrobial drug.

Graphical Abstract

Highlights

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  Structures of DPAGT1 with UDP-GlcNAc and tunicamycin reveal mechanisms of catalysis

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  DPAGT1 mutations in patients with glycosylation disorders modulate DPAGT1 activity

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  Structures, kinetics and biosynthesis reveal role of lipid in tunicamycin

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  Lipid-altered, tunicamycin analogues give non-toxic antibiotics against TB

Abstract

Structural insights into tunicamycin’s toxic interactions with the human N-linked glycosylation pathway allows the identification of non-toxic antibiotics effective against tuberculosis in mice