Epidermal growth factor receptor binding is not a simple one-step process.
The binding kinetics of 125I-labeled mouse epidermal growth factor (EGF) to receptors on human fibroblast cells in monolayer culture were measured at 4 degrees C. Initial binding rates as a function of hormone concentration allowed estimation of simple two-state on-off rate constants of 1.2 x 10(6) M-1 s-1 and 4.9 x 10(-3) s-1, respectively. These two-state parameters gave inadequate computer fits to long term kinetic and equilibrium-binding data, suggesting that an additional process(es) was occurring. Nonlinear equilibrium Scatchard plots and transient "pseudo-Scatchard" plots taken at pre-equilibrium times support the idea that at least one other process is occurring during receptor binding. 125I-EGF-receptor dissociation kinetic plots were biphasic, yielding rate constants of 1.5 x 10(-2) s-1 and 5.6 x 10(-5) s-1 with the ratio of the two components changing with the time of initial incubation with 125I-EGF. Application of a ternary complex model which assumed complexation of the bound receptor with a cell surface interaction molecule gave satisfactory fits to all data.
Mayo
K H
KH
Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122.
Nunez
M
M
Burke
C
C
Starbuck
C
C
Lauffenburger
D
D
Savage
C R
CR
D000818:Animals; D002478:Cells, Cultured; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008297:Male; D008433:Mathematics; D051379:Mice; D008962:Models, Theoretical; D011485:Protein Binding; D012867:Skin / Q000378:metabolism
D004815:Epidermal Growth Factor; D066246:ErbB Receptors