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Binding of the cSH3 domain of Grb2 adaptor to two distinct RXXK motifs within Gab1 docker employs differential mechanisms

Authors

  • Caleb B. McDonald,

    1. Department of Biochemistry & Molecular Biology, USylvester Braman Family Breast Cancer Institute, Leonard Miller School of Medicine, University of Miami, Miami, FL 33136, USA
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  • Kenneth L. Seldeen,

    1. Department of Biochemistry & Molecular Biology, USylvester Braman Family Breast Cancer Institute, Leonard Miller School of Medicine, University of Miami, Miami, FL 33136, USA
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  • Brian J. Deegan,

    1. Department of Biochemistry & Molecular Biology, USylvester Braman Family Breast Cancer Institute, Leonard Miller School of Medicine, University of Miami, Miami, FL 33136, USA
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  • Vikas Bhat,

    1. Department of Biochemistry & Molecular Biology, USylvester Braman Family Breast Cancer Institute, Leonard Miller School of Medicine, University of Miami, Miami, FL 33136, USA
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  • Amjad Farooq

    Corresponding author
    1. Department of Biochemistry & Molecular Biology, USylvester Braman Family Breast Cancer Institute, Leonard Miller School of Medicine, University of Miami, Miami, FL 33136, USA
    • Department of Biochemistry & Molecular Biology, USylvester Braman Family Breast Cancer Institute, Leonard Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
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Abstract

A ubiquitous component of cellular signaling machinery, Gab1 docker plays a pivotal role in routing extracellular information in the form of growth factors and cytokines to downstream targets such as transcription factors within the nucleus. Here, using isothermal titration calorimetry (ITC) in combination with macromolecular modeling (MM), we show that although Gab1 contains four distinct RXXK motifs, designated G1, G2, G3, and G4, only G1 and G2 motifs bind to the cSH3 domain of Grb2 adaptor and do so with distinct mechanisms. Thus, while the G1 motif strictly requires the PPRPPKP consensus sequence for high-affinity binding to the cSH3 domain, the G2 motif displays preference for the PXVXRXLKPXR consensus. Such sequential differences in the binding of G1 and G2 motifs arise from their ability to adopt distinct polyproline type II (PPII)- and 310-helical conformations upon binding to the cSH3 domain, respectively. Collectively, our study provides detailed biophysical insights into a key protein–protein interaction involved in a diverse array of signaling cascades central to health and disease. Copyright © 2010 John Wiley & Sons, Ltd.

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