FKBP1B, also known as peptidyl-prolyl cis-trans isomerase FKBP1B, is a member of the immunophilin protein family which plays a role in immunoregulation and basic cellular processes involving protein folding and trafficking. This protein is a cis-trans prolyl isomerase that binds the immunosuppressants FK506 (tacrolimus) and rapamycin (sirolimus). It is highly similar to the FK506-binding protein 1A. Its physiological role is thought to be in excitation-contraction coupling in cardiac muscle. Recombinant human FKBP1B protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography.