Conformational Dynamics in a Truncated Epidermal Growth Factor Receptor Ectodomain
Details
Publication Year 2011-06,Volume 50,Issue #23,Page 5130-5139
Journal Title
Biochemistry
Publication Type
Journal Article
Abstract
Structural studies have revealed two forms of the monomeric epidermal growth factor receptor (EGFR) ectodomain: a compact (tethered) form stabilized by interdomain interactions and an extended (untethered) form in the presence of ligand. An important question is whether the ligand induces a conformational transition from a tethered to untethered form or whether there is a preexisting conformational equilibrium between tethered and untethered states. To distinguish between these two possibilities, we investigated a truncated receptor, EGFR501 (spanning residues 1-501), that contains the minimal elements required for high-affinity ligand binding in solution. Conformational transitions and dynamics were inferred by means of fluorescence from five internal tryptophan residues that are located within or close to the ligand-binding domains of EGFR501. A preexisting conformational equilibrium between tethered and untethered states in EGFR501 was deduced from (1) the nonlinear Arrhenius temperature dependence of fluorescence and (2) fluorescence polarization showing independently mobile domains. In contrast, the ligand EGFR501 complex revealed a linear Arrhenius temperature dependence of fluorescence and increased fluorescence polarization due to a lack of significant interdomain motions. The data suggest that the role of the ligand is to trap the EGFR501 in the untethered state that is transiently formed in solution through a preexisting conformational equilibrium.
Publisher
ACS
Keywords
fluorescence-polarization spectrum; electronic-energy transfer; extracellular domain; egf receptor; crystal-structure; high-affinity; cell-surface; activation; proteins; binding
Research Division(s)
Structural Biology
Link To PubMed Central Version
http://pubs.acs.org/doi/abs/10.1021/bi200095w
Terms of Use/Rights Notice
Copyright © 2011 American Chemical Society


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