FK506 binding protein 1a, also known as FKBP12, belongs to the immunophilin protein family, which play a role in immunoregulation and basic cellular processes involving protein folding and trafficking. FKBP12 also plays a role in intracellular calcium regulation by associating with three types of calcium release channel complexes, cardiac and skeletal ryanodine receptors and the inositol 1,4,5-trisphosphate receptor. It interacts with several intracellular signal transduction proteins including type I TGF-beta receptor. Recombinant human FKBP12, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography.