Structural Dynamics upon directed Virus Glycan interaction

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Native mass spectrometry (MS) is very powerful in discriminating between different virus assembly states and monitoring virus stability. Additionally, binding affinities of viral assemblies to glycans can be derived by MS. Structural changes mediated by such ligand binding can be monitored by hydrogen/deuterium exchange (HDX) MS. We hypothesize that glycans, being multivalent attachment factors on cell surfaces, can trigger conformational transitions in viruses. These changes can prime for cellular uptake, open up new binding sites for secondary receptors or modify stability, facilitating intracellular uncoating. Recent findings indicate that glycan binding to noroviruses is a complex process involving widening of the binding site leading to further structural changes throughout the capsid protein. Since human noroviruses are well-studied by MS, we will use this system to establish binding affinity and stability assays in native MS. Then, we apply these protocols to murine noroviruses (MNV) where we can also study the infectious particle (Peters and Taube labs). We will also study the impact of multivalent glycan mimetics (Hartmann lab) and participate in ligand screens. Human noroviruses will be the first target to establish HDX MS. Native MS studies will inform HDX MS analysis and provide most promising glycans and concentrations to probe structural changes. Both techniques will be carried out under different conditions to compare how the assembly state and genome incorporation of the particles affect binding and structural transitions. We will also apply our pool of techniques to Merkel Cell Polyomavirus (MCPyV, Blaum) and human papillomavirus type 16 (HPV16, Schelhaas) binding to sialic acids and heparan sulfates. It is known that HPV16 undergoes glycan induced structural transitions. Glycan induced structural changes in MCPyV are so far unknown but appear possible for heparan sulfate binding by analogy with HPV16. In all cases, we can provide detailed structural information on virus dynamics upon glycan binding, which can inform design of inhibitors and diagnostic tools.