A post-translational modification of human Norovirus capsid protein attenuates glycan binding

Alvaro Mallagaray,Thomas Peters,Esben Trabjerg,Kasper D Rand,Jasmin Dülfer,Robert Creutznacher,Philipp H O Mayer,Jose Maria Orduña,Thilo Stehle,Charlotte Uetrecht,Lena Lisbeth Grimm,Bärbel S Blaum

doi:10.1038/s41467-019-09251-5

Abstract

Attachment of human noroviruses to histo blood group antigens (HBGAs) is essential for infection, but how this binding event promotes the infection of host cells is unknown. Here, we employ protein NMR experiments supported by mass spectrometry and crystallography to study HBGA binding to the P-domain of a prevalent virus strain (GII.4). We report a highly selective transformation of asparagine 373, located in an antigenic loop adjoining the HBGA binding site, into an iso-aspartate residue. This spontaneous post-translational modification (PTM) proceeds with an estimated half-life of a few days at physiological temperatures, independent of the presence of HBGAs but dramatically affecting HBGA recognition. Sequence conservation and the surface-exposed position of this PTM suggest an important role in infection and immune recognition for many norovirus strains.

Highlights

Attachment of human noroviruses to histo blood group antigens (HBGAs) is essential for infection, but how this binding event promotes the infection of host cells is unknown
Supplementary Note 2, Supplementary Figs. 5–8, and results from Dynamic Light Scattering (DLS) measurements, Supplementary Fig. 9). 1H,15N Transverse Relaxation Optimized Spectroscopy (TROSY) Heteronuclear Single Quantum Coherence (HSQC) spectra experiments showed that a substantial fraction of NH backbone signals was missing due to very slow exchange of backbone deuterons DN to HN
Our previous studies suggest that binding of human noroviruses to HBGAs involves cooperativity[19,22,43]

Summary

Introduction

Attachment of human noroviruses to histo blood group antigens (HBGAs) is essential for infection, but how this binding event promotes the infection of host cells is unknown. The NMR assignment exposed a highly specific deamidation of amino acid N373, resulting in an isopeptide linkage and causing a dramatic decrease of HBGA-binding affinity These NMR results were supported by crystallography and hydrogen/deuterium exchange MS (HDX MS). Sequence analysis of GII.[4] strains suggests that the modification is highly abundant, implying that previously published HBGA binding data may require careful revision Such a dramatic change in HBGA binding will have implications for the infection process and, due to the antigenicity of the affected region[27,28,29], very likely for the immune response

Methods

Results

Conclusion