Purification Of A 25kD Protein From Rapamycin Producing Strain Streptomyces Hygroscopicus ATCC 367817

FK506 Binding Proteins (FKBPs) is a family of proteins, which can directly bind the immunosupressant drugs FK506 and rapamycin. FKBPs exist in all the living cells and have many different functions. In this paper, a 25kD protein was purified from rapamycin producing strain Streptomyces hygroscopicus ATCC 367817 by DE-52 anion exchange chromatography and Sephadex G-50 gel filtration chromatography. The purity of the 25kD protein was detected by 15% SDS-PAGE. PPIase activity of the purified protein was determined. Rapamycin and FK506 appeared to be potent inhibitors of PPIase activity of the 25kD protein whereas cyclosporin A at a concentration of 1μM gave no inhibition. These results showed that the 25kD protein is a family member of FKBPs. In the competitive inhibition experiment, it showed that rapamycin and FK506 could bind this protein competitively and rapamycin had better binding capacity than FK506. The work done by this study provided methodology basis for further researches on establishing a model for screening new immunosupressants.