Interactions of human norovirus capsid P domain with histo-blood group antigens with Hydrogen-Deuterium Exchange Mass Spectrometry

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 employed protein NMR experiments supported by mass spectrometry and crystallography to study HBGA binding to the P domain of a prevalent virus strain (GII.4) in more detail . We report a highly selective transformation of N373, 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.