Chojnacki, M. et al. Cell Chem. Biol. doi:10.1016/j.chembiol.2017.02.013 (2017).

Multiple cellular processes are influenced by ubiquitination, the covalent attachment of chains of ubiquitin molecules to proteins. Because ubiquitination is so prevalent in cells, and because different ubiquitin chain structures result in different cellular signals, this post-translational modification is challenging to study. Chojnacki et al. describe Ub-phototrap tools as an approach to detect ubiquitin-binding interactions. The Ub-phototrap is a ubiquitin variant containing a photoactivatable crosslinker as an unnatural side chain, allowing ubiquitin binding domains to be captured and then identified. Chojnacki et al. created a series of Ub-phototrap reagents with distinct linkages and lengths. Applying these tools to the 26S proteasome complex, the researchers trapped Rpn10 and Rpn13, known ubiquitin-binding domains, and Rpn1, which was previously unknown. They followed up with NMR experiments to identify the binding region.