Purification and characterization of a feline hepatic insulin receptor

Objective—To elucidate the functional characteristics of a highly purified soluble liver insulin receptor in cats. Sample population—Frozen livers from domestic cats were obtained commercially. Procedures—The feline hepatic insulin receptor was purified from Triton X-100 solubilized plasma membranes by the use of several chromatography matrices, including affinity chromatography on an insulin-Sepharose matrix. Results—The receptor, although not homogeneous, was purified 3,000-fold. Two silver-stained protein bands were identified following sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE) with molecular weight of 134,000 and 97,000, which are similar to insulin receptors isolated from other animals. This isolated receptor had steady-state insulin binding by 40 minutes at 24 C. Optimal insulin binding occurred at pH 7.8 and with 150 mM NaCl. Under these conditions, a curvilinear Scatchard plot was obtained with the isolated receptor. Using a 2 bindingsite model, the feline insulin recep...