Purification and characterization of cyclosporine and FK-506 binding proteins from a human T-helper cell line.

Cytosolic proteins that specifically bind cyclosporine A and FK-506 were isolated and purified from the JURKAT human T-helper cell line. These binding proteins were purified by affinity, molecular weight exclusion and weak cation exchange column chromatography. Radiolabeled cyclosporine A specifically bound to a approximately 17 kDa molecule which is cyclophilin and also bound to a approximately 50 kDa protein(s). Radiolabeled FK-506 did not bind to the approximately 17 kDa molecular weight protein, but specifically bound to soluble approximately 10 kDa and approximately 50 kDa proteins.