Lysine Targeting Group‐Transfer Chimeras for Proximity Induction

Abstract Nature employs post‐translational modifications (PTMs) to induce proximity between proteins by engendering new interactions. Furthermore, we find that protein ligands are invariably proximal to a lysine. Inspired by these two observations, we developed group‐transfer chimeras (GRCs) that append a moiety‐of‐interest to the lysine side chain. GRCs employ a protein's ligand and a handle with a transferase ‐type reactivity to modify the proximal lysine. Contemporary lysine‐targeting group‐transfer handles were incompatible with GRCs due to their hydrolytic instability, large size, high reactivity, and synthetic incompatibility with diverse ligands. Accordingly, we developed an N ‐( su lfonyl)‐ N ‐(tri f luoroethyl)‐ethan a mide (SuFA) handle that is stable, small, and exhibits tunable reactivity and synthetic compatibility with diverse ligands and proteins. Using GRCs that group‐transfer binders of tags (e.g., HaloTag, FKBP) onto proteins overexpressed in cancer cells, we displayed these binders on the surface of the cancer cell. With a un iversal T cell e ngager (UniTE) that binds to the displayed ligands and T cells, these GRCs induced proximity between cancer cells and cytotoxic T cells, leading to the latter's activation. We envision the GRC platform to find utility in basic research and biomedicine.