On the binding of dolichol by bovine liver supernatant.

Experimental evidence is presented that a bovine liver pH 5.1 supernatant possesses binding capacity towards dolichol. Optimal binding is found at physiological pH and at 5 degrees C. At higher temperature the binding is drastically reduced. After binding, the labelled ligand cannot be chased by unlabelled dolichol. Scatchard analysis indicates a single class of binding sites (Bmax = 3.6 pmol/mg protein) with an apparent Kd of 1.8 X 10(-11) M. Only dolichol and dolichyl derivatives drastically reduce the binding phenomenon. The involvement of a protein-like structure is inferred from ammonium sulphate precipitation and proteolysis experiments. Exclusion chromatography and gel electrophoresis under nondenaturating conditions indicate a high molecular weight of the binding complex. Upon SDS electrophoresis, bound [3H]dolichol comigrates with a single protein band (Mr approximately equal to 25,000).