Figure 3.

Principle of orthogonal receptor-ligand pairs and the cellular thermal shift assay (CETSA). A, Orthogonal receptor-ligand pairs can be designed from an endogenous receptor, which is capable of binding the endogenous ligand (yellow) but not the ligand of interest (blue), which lacks activity in the biological system of interest. Receptor engineering results in the inability of the endogenous ligand to activate the engineered receptor, which is now activated by the ligand of interest. B, The CETSA principle is based on the small molecule-mediated stabilization or destabilization of the protein target (yellow cartoon and curves) relative to the unbound protein target (blue cartoon and curve), as measured by thermal denaturation of the protein of interest (black cartoons, curves).