Self-phosphorylation of epidermal growth factor receptor is an intermolecular reaction.
The binding of epidermal growth factor (EGF) to epidermal growth factor receptor (EGF receptor) results in the dimerization and self-phosphorylation of the receptor. Both of these responses were followed as a function of time and the concentration of EGF receptor. Dimerization of EGF receptor was monitored by immunoblotting the protein after it had been cross-linked with glutaraldehyde. The capacity for self-phosphorylation was followed by measuring the relative level of incorporation of [32P]phosphate into EGF receptor on autoradiograms of the same immunoblots used for the assay of its dimerization. When these two properties were followed as a function of time, it was found that dimerization preceded the appearance of the capacity for self-phosphorylation. Both dimeric and monomeric forms of EGF receptor were self-phosphorylated in the presence of EGF, but the dimeric form was phosphorylated preferentially to the monomeric form. When the dimerization and the capacity for self-phosphorylation were followed as a function of the concentration of dimeric EGF receptor, it was observed that the self-phosphorylation of dimeric EGF receptor increased as the concentration of dimeric EGF receptor increased. An equation including terms representing both intramolecular and intermolecular rates of self-phosphorylation was fit to the plots of self-phosphorylation as a function of concentration of EGF receptor. These fits demonstrate that intramolecular self-phosphorylation within dimers of EGF receptor is insignificant and that self-phosphorylation is an intermolecular process between dimers of EGF receptor.
Sherrill
J M
JM
Department of Chemistry and Biochemistry 0506, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093-0506, USA.
D000255:Adenosine Triphosphate / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell; D003432:Cross-Linking Reagents; D019281:Dimerization; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D005976:Glutaral; D006801:Humans; D007700:Kinetics; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D011865:Radioisotope Dilution Technique; D014407:Tumor Cells, Cultured
D003432:Cross-Linking Reagents; D010761:Phosphorus Radioisotopes; D004815:Epidermal Growth Factor; D000255:Adenosine Triphosphate; D066246:ErbB Receptors; D005976:Glutaral