Purification of the insulin receptor protein from porcine liver membranes

Insulin receptor protein was isolated from porcine liver membranes. Starting with 600 g of liver, the plasma membrane-enriched fraction with extracted with detergent. After AcA 34 gel chromatography, affinity chromatography and DEAE-Sephacel chromatography an insulin receptor preparation was obtained which was 2500-fold purified over crude homogenate and which had a specific binding activity of up to 1 x 10(-9) mol insulin/mg protein. The yield was 200 micrograms. Analysis of binding data according to Scatchard resulted in curvilinear plots and substantially the same affinity constants with the membrane preparation and also with the purified insulin receptor protein. Dodecyl sulfate gradient gel electrophoresis of the purified insulin receptor protein showed up to eight protein bands in the range from 38 to 175 kDa. The main bands indicate an apparent molecular mass of 38, 60, 80, 120 and 150 kDa for the insulin receptor-binding protein subunits.