Target-Templated Construction of Functional Proteomimetics Using Photo-Foldamer Libraries

Current methods for proteomimetic engineering rely on structure-based design. Here we describe a design strategy that allows the construction of proteomimetics against challenging targets without a priori characterization of the target surface. Our approach employs (i) a 100-membered photoreactive foldamer library, the members of which act as local surface mimetics, and (ii) the subsequent affinity maturation of the primary hits using systems chemistry. Two surface-oriented proteinogenic side chains drove the interactions between the short helical foldamer fragments and the proteins. Diazirine-based photo-crosslinking was applied to sensitively detect and localize binding even to shallow and dynamic patches on representatively difficult targets. Photo-foldamers identified functionally relevant protein interfaces, allosteric and previously unexplored targetable regions on the surface of STAT3 and an oncogenic K-Ras variant. Target-templated dynamic linking of foldamer hits resulted in two orders of magnitude affinity improvement in a single step. The dimeric K-Ras ligand mimicked protein-like catalytic functions. The photo-foldamer approach thus enables the highly efficient mapping of protein-protein interaction sites and provides a viable starting point for proteomimetic ligand development without a priori structural hypotheses.