The RCAN carboxyl end mediates calcineurin docking-dependent inhibition via a site that dictates binding to substrates and regulators.
Martinez-Martinez S, Genesca L, Rodriguez A, Raya A, Salichs E, Were F, Lopez-Maderuelo MD, Redondo JM, de la Luna S, Proc Natl Acad Sci U S A, 2009 Apr 14 - link

A conserved docking surface on calcineurin mediates interaction with substrates and immunosuppressants.
Rodriguez A, Roy J, Martinez-Martinez S, Lopez-Maderuelo MD, Nino-Moreno P, Orti L, Pantoja-Uceda D, Pineda-Lucena A, Cyert MS, Redondo JM, Mol Cell, 2009 Mar 13 - link