Figure 1 - The immunosuppressive compound rapamycin bound to FKBP12 and the FRB domain of mTOR.

FKBP12 is represented by the blue ribbon diagram on the left, the FRB domain of mTOR is represented by the green ribbon diagram on the right, and rapamycin is shown as individual spheres. Rapamycin simultaneously binds these two proteins by having different parts of the molecule fill hydrophobic pockets in each protein while the more polar region of rapamycin is concentrated on a small solvent-exposed surface between the two proteins.