Epidermal growth factor receptor dimerization and activation require ligand-induced conformational changes in the dimer interface.
Structural studies have shown that ligand-induced epidermal growth factor receptor (EGFR) dimerization involves major domain rearrangements that expose a critical dimerization arm. However, simply exposing this arm is not sufficient for receptor dimerization, suggesting that additional ligand-induced dimer contacts are required. To map these contributions to the dimer interface, we individually mutated each contact suggested by crystallographic studies and analyzed the effects on receptor dimerization, activation, and ligand binding. We find that domain II contributes >90% of the driving energy for dimerization of the extracellular region, with domain IV adding little. Within domain II, the dimerization arm forms much of the dimer interface, as expected. However, a loop from the sixth disulfide-bonded module (immediately C-terminal to the dimerization arm) also makes a critical contribution. Specific ligand-induced conformational changes in domain II are required for this loop to contribute to receptor dimerization, and we identify a set of ligand-induced intramolecular interactions that appear to be important in driving these changes, effectively "buttressing" the dimer interface. Our data also suggest that similar conformational changes may determine the specificity of ErbB receptor homo- versus heterodimerization.
Dawson
Jessica P
JP
Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, 19104-6059, USA.
Berger
Mitchell B
MB
Lin
Chun-Chi
CC
Schlessinger
Joseph
J
Lemmon
Mark A
MA
Ferguson
Kathryn M
KM
D001665:Binding Sites; D019281:Dimerization; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D020349:Surface Plasmon Resonance; D016211:Transforming Growth Factor alpha / Q000494:pharmacology
D008024:Ligands; D016211:Transforming Growth Factor alpha; D066246:ErbB Receptors