Crystal structures of wild-type and HC CypB. A. Cα ribbon presentation of horse wild-type (green) and HC (red) CypB. Chain displacement is observed within the N-terminal tail (residues from Ala(−1) to Pro7) B. Superimposed active site of horse wild-type (green), HC (red) and human (yellow; PDB: 1CYN ) CypB. Cyclosporin A is shown as ribbon (blue), which is a part of the complex with human CypB. Sidechains of residues that contribute to the binding of cyclosporin A are shown as sticks. C. Electron density maps for wild-type and HC CypB molecules calculated using 2Fo-Fc coefficients contoured at 1.0σ and shown in gray. D. Refined residue occupancy values of the N-terminal sequence for the wild-type (green) and HC (red) CypB models. E. Refined Cα B factors of the N-termini for the wild-type (green) and HC (red) CypB models. F. Stereo pair of superimposed structures of horse wild-type CypB (green), HC CypB (magenta) and the human CypB (yellow) complexed with the P-domain of calmegin  (white).