title: p-Azidophenylglyoxal-epidermal growth factor: a photoactivatable affinity crosslinking reagent.
abstract: A photoaffinity derivative of highly purified 125I-labelled epidermal growth factor (125-I-EGF) has been synthesized. The heterobifunctional crosslinking reagent p-azidophenylglyoxal (PAPG) was bound to arginine residues in 125I-EGF. PAPG-125 I-EGF bound to EGF receptors on rat fibroblasts and human A431 epidermoid carcinoma cells in culture. An apparent decreased affinity of PAPG-125I-EGF for the EGF receptor is in accord with at least one arginine being at or near the EGF receptor binding site. The PAPG-125I-EGF:EGF receptor complexes on rat cells were internalized to the same extent as control EGF:receptor complexes. A431 cells treated with PAPG-125I-EGF were irradiated with ultraviolet light and the labelled proteins were analyzed by SDS-polyacrylamide gel electrophoresis. The 3 major labelled proteins had apparent molecular weights ranging from 75,000 to 200,000. Only the labelling of the 200,000-Mr protein was prevented by the addition of excess unlabelled EGF with the PAPG-125I-EGF. This molecular weight is in agreement with the reported size of the EGF receptor plus EGF. A protein with apparent molecular weight of 100,000 was labelled by 125I-EGF by an unknown mechanism which was dependent on the dose of UV light and blocked by the addition of excess unlabelled EGF.
mesh_terms: D000447:Aldehydes / Q000138:chemical synthesis*; D000818:Animals; D001386:Azides / Q000138:chemical synthesis*; D002460:Cell Line; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D004815:Epidermal Growth Factor / Q000502:physiology*; D066246:ErbB Receptors; D005347:Fibroblasts / Q000187:drug effects; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D010658:Phenylglyoxal / Q000031:analogs & derivatives / Q000138:chemical synthesis*; D051381:Rats; D011956:Receptors, Cell Surface
chemical_list: D000447:Aldehydes; D001386:Azides; D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D004815:Epidermal Growth Factor; C032404:4-azidophenylglyoxal; D066246:ErbB Receptors; D010658:Phenylglyoxal