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.