Project Summary The protein‐protein interaction network that form between transcriptional coactivators and activators is dysregulated in every human disease as either a cause or an effect and as such represents a potentially powerful intervention point for therapeutic development. Yet there is little knowledge about this PPI network, particularly how binding events in one domain of a coactivator impacts the global structure and function of the remainder of the domains. We demonstrated in earlier work funded by NIGMS that we can take advantage of the conformational plasticity of coactivators to discover covalent chemical co‐chaperones and small molecules that capture distinct conformational suites of coactivators in vitro and in the cellular milieu. Thus we are poised to answer fundamental questions regarding coactivators: how does a local binding event at an ABD (known to change dynamics and local structure) affect the PPI network of the coactivator, global structural dynamics, and ultimately function. This will not only increase the resolution of our understanding of the basic biology of transcription but also provide a framework by which predictions for the best PPIs for transcription‐targeted therapeutics can be made. Building on the tools and strategies developed in our GM‐funded work, we will define the molecular recognition rules for coactivator ABDs. In doing so, we will produce a suite of selective modulators for functionally distinct coactivators. These data will also provide a rigorous framework and predictive algorithm for the future discovery of selective small molecules and peptidomimetic inhibitors. Through structural studies of intact coactivator‐activator complexes, we will expand the molecular recognition model to include the relationship between local binding‐induced conformational changes and global architectural and functional alterations within full‐length activators and coactivators. We request a replacement for our current automated peptide synthesizer (purchased in 2016) in order to accomplish the goals of the grant, particularly for Project 2. The model we are requesting also has the capability of synthesizing up to four peptides/peptidomimetics sequentially, leading to enormous efficiencies since we can then use the instrument in overnight runs. This will significantly facilitate the accomplishment of the project and due to the unanticipated nature of the need and the price of such an instrument, it cannot be accommodated in the budget of GM136356.