Chaperone-like activity of immunophilin FKBP12 from bovine brain, a cytoplasmic receptor of immunosuppressor FK506

The chaperone-like activity of brain immunophilin—a cytoplasmic receptor of immunosuppressor FK506 (FK506-binding protein, FKBP12) was evaluated in a test-system in vitro based on suppression of insulin aggregation as a result of A-and B-chain dissociation induced by disulfide bond reduction by dithiotreitol. Using dynamic light scattering technique we have demonstrated the concentration dependent suppression of light scattering intensity and the decrease of the hydrodynamic radius of insulin B-chain amorphous aggregates upon addition of FKBP12 to the incubation medium, a significant effect being revealed even in the substoichiometric concentration range. The results provide evidence that FKBP12 possesses chaperone-like activity preventing insulin aggregation.