Identification of the insulin receptor in plasma membranes of Ehrlich ascites carcinoma cells by photoaffinity labeling.

Binding of 125I-insulin to Ehrlich ascites carcinoma cells revealed the presence of high affinity binding sites characterized by a dissociation constant of 6.1 . 10(-9) M and a number of sites per cell of 2.6 . 10(3). These values are in line with respective data for other cell types reported in the literature. The receptor was identified by photoaffinity labeling of highly purified plasma membranes with 4-azido-benzoyl-125I-insulin as a probe. The only receptor protein detectable has a molecular mass of 120-122 kD. This finding is discussed in terms of metabolic and cell proliferation effects of insulin.