Capturing post-translational modification-triggered protein-protein interactions using dual noncanonical amino acid mutagenesis.

Reversible post-translational modification (PTM) is a powerful and ubiquitous mechanism to regulate protein function. The mechanistic basis of the associated functional regulation by PTMs often involves the recruitment of interaction partners that selectively binds the modified protein. Identifying such functionally important protein-protein interactions that are uniquely triggered by PTMs remains difficult due to several technical challenges. To address this, here we develop technology to site-specifically incorporate two distinct noncanonical amino acids into recombinant proteins: one modeling a PTM of interest and the second harboring a photoaffinity probe. Using lysine-23 acetylation of histone 3 as a model system, we show that such dual-labeled "protein probes" can covalently capture its "reader" protein.