Location of mutated residues. (A) Crystallographic representation of the heterodimer of CNa (blue chain) and CNb (red chain). Mutated residues of CNa and CNb are shown in gray and yellow, respectively. (B) Reverse projection crystallographic representation of heterodimer of FKBP12 and FK506. CNa/b chains are included for orientation. Mutated residues of FKBP12 are shown in white.