Minde, D.-P. et al. Commun. Biol. 3, 38 (2020).

Proteins implicated in diseases such as neurodegeneration, cancer and heart-related disorders are often rich in intrinsically disordered regions (IDRs); however, these proteins remain challenging to study. In particular, the in vivo malleability of these disordered regions, which allows them to adopt different structural forms under different cellular states, has barely been characterized. Minde et al. show through proximity proteomics studies that biotin proximity tagging occurs more favorably in IDRs than in the folded regions of a protein. The researchers further evaluated the time dependence of biotinylation in Escherichia coli ribosomes, in a technique they call ‘biotin painting’. Biotin labeling was performed for different lengths of time and quantified, providing an estimate of the time course of the structural plasticity of these molecules ranging from unfolded and exposed regions to structured and shielded regions. The assay could be used to obtain in vivo dynamics of intrinsically disordered proteins.