Orthogonal ligand-protein pair
Orthogonal ligand-protein pairs (also known as re-engineered ligand-receptor interfaces or re-engineered enzyme-substrate interactions) are a protein-ligand binding pair made to be independent of the original binding pair. This is done by taking a mutant protein (naturally occurring or selectively engineered), which is activated by a different ligand (carefully synthesized or selected).
Source: Wikipedia — Orthogonal ligand-protein pair (CC BY-SA 4.0)