HDX-MS of Human Histidine Rich Glycoprotein (HRG)

Histidine rich glycoprotein (HRG) is a multi-domain plasma glycoprotein, which is implicated in numerous biological processes including immune regulation, angiogenesis, coagulation and fibrinolysis. Despite a diverse role of biological functions, structural investigations into HRG have yielded only limited information, and there are no 3-dimensional structures of the intact protein. Current computational modelling suggests that HRG exhibits a large degree of conformational flexibility, which likely contributes to its well-documented multifunctionally. Here, utilising amide hydrogen-deuterium exchange mass spectrometry (HDX-MS), and combining insights from AlphaFfold, we investigate the conformational landscape of HRG. Overall, our data reveal a high degree of H/D exchange within the HRR, PRR and C terminal domains, indicating these regions are exposed to the aqueous environment surrounding the HRG surface, and provides the strongest evidence yet that these are largely disordered in vivo. Overall, this investigation lays the foundation for understanding the conformational architecture of HRG and paves the way for future studies aimed at elucidating how the interactions between HRG and other molecules are mediated, potentially revealing new mechanisms of its biological activity.