RELEASE OF HYDROPHOBIC LIGAND FROM RETINOL-BINDING PROTEIN UNDER CONDITIONS MIMICKING THE MEMBRANE FIELD

The plasma retinol-binding protein (REP) can release its hydrophobic l igand retinol (vitamin A) under low pH and low solvent dielectric cons tant (various mixtures of low ionic strength buffer with methanol). Us ing near-and far-UV circular dichroism, fluorescence, and macroscopic diffusion, release of retinol was shown to be attended with a conforma tional transition of REP from the native state to a molten globule-lik e one. The electric properties of the denaturing media used to release retinol iii vitro, were close to those occurring in vivo near the sur face of a negatively charged membrane.