EPR spectroscopic characterisation of native Cu^II-binding sites in human serum albumin

Human serum albumin (HSA) is the most abundant plasma protein, which functions to transport a large range of ligands within the circulation. These interactions have important implications for human health and disease. The primary binding site for Cu^II ions on HSA is known to be the so-called amino-terminal Cu^II and Ni^II binding (ATCUN) motif. However, the number and identity of secondary binding sites is currently not understood. In this study, we harnessed a suite of contemporary electron paramagnetic resonance (EPR) spectroscopy methods to investigate recombinantly produced constructs of HSA bearing single-histidine knockouts, with the aim to characterise its endogenous Cu^II ion binding sites.