ISOLATION AND PARTIAL CHARACTERIZATION OF A WATER-SOLUBLE RECEPTOR PROTEIN OF INSULIN

<正> By using the chelate EDTA at low concentration to remove the bivalent cations in the plasma membranes and followed by n-butanol to extract the membrane lipids, we have obtained a water-soluble insulin receptor without detergent from the liver-cell plasma membranes.This receptor protein does not precipitate by eentrifugation at 300,000×g for 70 min, nor does it retain on 0.22 micron millipore filter. Tt does not retard on Sephadex G-200 gel chromatographic column either. It is thus proved that the insulin-receptor protein obtained by this method is completely soluble in water.The dissociation constant of the water-soluble receptor of insulin at 24℃ is calculated to be 3.6 × 10-9 M and its isoelectric point was approximately pH 4.1. As the fluorescence hydrophobic probe 1,8-ANS does not significantly affect the binding activity between the receptor and the insulin, it seems that in addition to a hydrophobic binding mechanism, there may exist some other forces of interaction.