Banci, L. et al. Nat. Chem. Biol. doi:10.1038/nchembio.1202 (3 March 2013).

The unique technique of in-cell nuclear magnetic resonance (NMR) allows proteins to be observed at atomic resolution under close-to-physiological conditions. In contrast to the highly artificial environment of a purified protein (as is typical for structural studies), in-cell NMR can yield a more realistic picture of how a protein actually behaves in the cell. Banci et al. report improvements to the in-cell NMR technique that allowed them to follow the complete post-translational maturation process of human protein superoxide dismutase 1 (SOD1), which defends the cell against oxidative stress. These improvements included expressing the protein in human cells at near-physiological concentrations, optimizing conditions to maintain cell viability in the NMR tube and increasing the sensitivity of the NMR measurements. The authors observed the processes of zinc and copper binding in SOD1 and found that the copper chaperone for SOD1 promotes disulfide bond oxidation.