Research in the Struwe Group centres on untangling the diverse and complex structure-function relationships of protein-linked oligosaccharides through the development of techniques that span protein engineering, chemical biology and mass spectrometry. Oligosaccharides, or glycans, are not only structurally diverse and contribute to remarkable protein heterogeneity but can be viewed as chemical elements that fine-tune protein biophysical properties and biomolecular interactions to various degrees.
The work we do focuses on host-pathogens interactions, principally among enveloped viruses, and our goal is to pin-point individual glycan structures, present among hundreds if not thousands of forms, responsible for discrete biological disease processes via the multivalent interactions they facilitate, including in receptor binding, immune recruitment and inflammation. A chemical understanding of such interactions is vital for designing next-generation therapeutics. Our approach is interdisciplinary but largely based on advanced methods in mass spectrometry and glycoprotein engineering strategies that enable us to study glycoprotein dynamics and transient, yet specific, glycan-dependent interactions.
Gas-phase glycoconjugate structural biology of viral glycoproteins
Deciphering virus glycoprotein structure is not only fundamental to our research but remains one of the most challenging aspects across biology due to inherent layers of structural complexity that ultimately limits our ability to study glycan-dependent interactions, including among neutralising antibodies. We address this problem by exploiting the gas-phase behaviour of oligosaccharides to facilitate their structural characterisation, including topology, linkage and branching, using ion mobility mass spectrometry (i.e. glycomics). Specifically, we leverage adduct formation and the three-dimensional conformation space occupied by individual glycans to separate isomeric structures present within complex biological mixtures. We extend these observations to the glycopeptide equivalent in detailed site-specific analyses that informs on both glycan structure and the amino acid site of attachment and therefore atomic structural detail of protein glycosylation (i.e. glycoproteomics).
Harnessing metabolic engineering for visualising glycoprotein interaction dynamics
A second aspect of our research is metabolic glycoprotein engineering and its application in two key areas. The first is its use to uncover protein glycosylation crosstalk or the degree to which a given protein is modified by glycans. We do this by manipulating the cellular machinery in the glycosylation pathway, either chemically or genetically, to produce homogeneous glycoproteins that we can measure by native mass spectrometry. We first demonstrated the potential of this approach by quantifying glycan occupancy on the HIV gp120 glycoprotein. We have also developed a novel strategy termed “native exoglycosidase sequencing mass spectrometry” to achieve similar results that uses glycan digesting enzymes to simplify natural occurring protein glycoforms. Our second glycoprotein engineering approach entails the incorporation of non-natural monosaccharides into glycoproteins during their biosynthesis. These monosaccharides display tags, present at different sites within a glycan or at discrete sites on a glycoprotein, that we use to trap weak, transient interactions or conformational dynamics that we can measure via chemical crosslinking mass spectrometry with spaciotemporal resolution.
Controlling glycoprotein bioconjugation on therapeutic drugs
We are also interested in developing glycoprotein-based drugs, specifically via precision antibody-drug conjugation. Here, we leverage the incorporation of chemical tags as above plus protein architecture to control antibody glycosylation. This permits us to directly manage the number of tags that can be used for conjugating cytotoxic drugs, DNA or fluorophores for cellular imaging, diagnostics or therapeutics.
I am a UKRI Future Leaders Fellow based in the Department of Chemistry and Kavli Institute for NanoScience Discovery. Prior to taking up my fellowship, I was Chief Scientific Officer of Refeyn, a University of Oxford spin-out based on mass photometry - a single molecule mass imaging technique I helped establish. I have been in Oxford since 2012, in both the Chemistry and Biochemistry Departments as a Post-Doctoral Researcher and Senior Research Associate where I studied the molecular mechanisms by which viruses glycosylate their surface proteins and developed new ways to understand how oligosaccharides interact with host receptors, innate immune lectin receptors and anti-viral lectins. Prior to moving to Oxford, I worked at the newly formed National Institute for Research and Training (NIBRT), a non-profit institute established to support research and education in biopharma globally. At NIBRT, I had the opportunity to work closely with a number of biotherapeutic companies to address various challenges in the analysis and process development of protein-based drugs. I obtained my B.S. from the University of Wisconsin, Madison and Ph.D. from the University of New Hampshire.
