Allostery mediates ligand binding to Grb2 adaptor in a mutually exclusive manner

• Published in: Journal of molecular recognition 2013-02, Vol.26 (2), p.92-103
• Main Authors: McDonald, Caleb B., El Hokayem, Jimmy, Zafar, Nawal, Balke, Jordan E., Bhat, Vikas, Mikles, David C., Deegan, Brian J., Seldeen, Kenneth L., Farooq, Amjad
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing - chemistry; Adaptor Proteins, Signal Transducing - genetics; Adaptors; allosteric control; Allosteric Regulation; Amino Acid Motifs; Binding; Binding Sites; Cellular; Escherichia coli - genetics; GRB2 Adaptor Protein - chemistry; GRB2 Adaptor Protein - genetics; Humans; intrinsic disorder; Kinetics; Ligands; Molecular Docking Simulation; Molecular Dynamics Simulation; Molecular Sequence Data; Multivalent binding; Nucleotides; Protein Binding; Protein Interaction Domains and Motifs; Protein Multimerization; Protein Structure, Secondary; Recognition; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Signal Transduction; SOS1 Protein - chemistry; SOS1 Protein - genetics; steric hindrance; Stoichiometry; Thermodynamics; Vices
• ISSN: 0952-3499; 1099-1352
• DOI: 10.1002/jmr.2256

Allostery plays a key role in dictating the stoichiometry and thermodynamics of multi‐protein complexes driving a plethora of cellular processes central to health and disease. Herein, using various biophysical tools, we demonstrate that although Sos1 nucleotide exchange factor and Gab1 docking protein recognize two non‐overlapping sites within the Grb2 adaptor, allostery promotes the formation of two distinct pools of Grb2–Sos1 and Grb2–Gab1 binary signaling complexes in concert in lieu of a composite Sos1–Grb2–Gab1 ternary complex. Of particular interest is the observation that the binding of Sos1 to the nSH3 domain within Grb2 sterically blocks the binding of Gab1 to the cSH3 domain and vice versa in a mutually exclusive manner. Importantly, the formation of both the Grb2–Sos1 and Grb2–Gab1 binary complexes is governed by a stoichiometry of 2:1, whereby the respective SH3 domains within Grb2 homodimer bind to Sos1 and Gab1 via multivalent interactions. Collectively, our study sheds new light on the role of allostery in mediating cellular signaling machinery. Copyright © 2013 John Wiley & Sons, Ltd. HIGHLIGHTS Binding of Grb2 to both Gab1 and Sos1 is governed by 2:1 stoichiometry Binding of Gab1 to Grb2 sterically blocks the binding of Sos1 and vice versa Such competitive binding results in the formation of two binary complexes in lieu of a composite ternary complex Ligand binding to Grb2 appears to be under tight allosteric control