title: Single-molecule analysis of epidermal growth factor binding on the surface of living cells.
abstract: Global cellular responses induced by epidermal growth factor (EGF) receptor (EGFR) occur immediately with a less than 1% occupancy among tens of thousands of EGFR molecules on single cell surface. Activation of EGFR requires the formation of a signaling dimer of EGFR bound with a single ligand to each molecule. How sufficient numbers of signaling dimers are formed at such low occupancy rate is still not known. Here, we have analyzed the kinetics of EGF binding and the formation of the signaling dimer using single-molecule imaging and mathematical modeling. A small number of EGFR on the cell surface formed dimeric binding sites, which bound EGF two orders of magnitude faster than the monomeric binding sites. There was a positive cooperative binding of EGF to the dimeric binding sites through a newly discovered kinetic intermediate. These two mechanisms facilitate the formation of signaling dimers of EGF/EGFR complexes.
authors.affiliation: Laboratories for Nanobiology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Teramura
authors.forename: Junya
authors.initials: J
authors.lastname: Ichinose
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Takagi
authors.forename: Kenji
authors.initials: K
authors.lastname: Nishida
authors.forename: Toshio
authors.initials: T
authors.lastname: Yanagida
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Sako
mesh_terms: D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D019281:Dimerization; D004815:Epidermal Growth Factor / Q000737:chemistry / Q000378:metabolism*; D066246:ErbB Receptors / Q000737:chemistry / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008954:Models, Biological; D008958:Models, Molecular; D046912:Multiprotein Complexes; D020836:Protein Structure, Quaternary; D015398:Signal Transduction
chemical_list: D046912:Multiprotein Complexes; D004815:Epidermal Growth Factor; D066246:ErbB Receptors