Rat liver cytosol oxysterol-binding protein. Characterization and comparison with the HTC cell protein

A cytosol protein that specifically binds cholesterol derivatives oxygenated on the side chain has been demonstrated in rat liver and transformed HTC cells. This protein, of which the sedimentation coefficient is about 8 S, was saturable and showed a high binding affinity (Kd about 5 X 10(-9) M) for 25-hydroxycholesterol. Its molecular mass is about 160 kDa. The physicochemical characteristics of this protein were identical whether the model was normal or transformed. This oxysterol-binding protein differs from the well-known sterol carrier proteins.