Structures of Grb2-SH2 Domain and AICD peptide Complexes Reveal a Conformational Switch and Their Functional Implications.
[GRB2_HUMAN] Adapter protein that provides a critical link between cell surface growth factor receptors and the Ras signaling pathway.   Isoform 2 does not bind to phosphorylated epidermal growth factor receptor (EGFR) but inhibits EGF-induced transactivation of a RAS-responsive element. Isoform 2 acts as a dominant negative protein over GRB2 and by suppressing proliferative signals, may trigger active programmed cell death.  
Publication Abstract from PubMed
It has been hypothesized previously that synergistic effect of both amyloid precursor protein intracellular C-terminal domain (AICD) and Abeta aggregation could contribute to Alzheimer's disease pathogenesis. Structural studies of AICD have found no stable globular fold over a broad range of pH. Present work is based on the premises that a conformational switch involving the flipping of C-terminal helix of AICD would be essential for effective binding with the Src homology 2 (SH2) domain of growth factor receptor binding protein-2 (Grb2) and subsequent initiation of Grb2-mediated endo-lysosomal pathway. High-resolution crystal structures of Grb2-SH2 domain bound to AICD peptides reveal a unique mode of binding where the peptides assume a noncanonical conformation that is unlike other structures of AICD peptides bound to protein-tyrosine-binding domains or that of its free state; rather, a flipping of the C-terminal helix of AICD is evident. The involvement of different AICD residues in Grb2-SH2 interaction is further elucidated through fluorescence-based assays. Our results reveal the significance of a specific interaction of the two molecules to optimize the rapid transport of AICD inside endosomal vesicles presumably to reduce the cytotoxic load.
Functional Implications of the Conformational Switch in AICD Peptide upon Binding to Grb2-SH2 Domain.,Das S, Raychaudhuri M, Sen U, Mukhopadhyay D J Mol Biol. 2011 Oct 4. PMID:22001015
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