Solution structure of the human Grb7-SH2 domain/erbB2 peptide complex and structural basis for Grb7 binding to ErbB2

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• The human Grb7-SH2 domain is a key signaling molecule involved in cellular processes.
• Understanding its interaction with ligands like erbB2 is crucial for deciphering signaling pathways.
• Receptor tyrosine kinases, such as erbB2, play significant roles in cell growth and cancer.

Purpose of the Study:

• To determine the solution structure of the human Grb7-SH2 domain bound to a phosphorylated erbB2 peptide.
• To investigate the structural basis of this interaction and compare it with other SH2 domain-ligand complexes.
• To analyze the influence of specific structural features, like insertions, on binding conformation.

Main Methods:

• Nuclear magnetic resonance (NMR) spectroscopy was used to determine the three-dimensional structure.
• A ten amino acid phosphorylated peptide representing erbB2 (pY1139) was used as the ligand.
• Structural analysis focused on the SH2 domain topology, ligand binding conformation, and residue interactions.

Main Results:

• The solution structure of the hGrb7-SH2 domain/pY1139 peptide complex was elucidated.
• The hGrb7-SH2 domain exhibits a canonical Src homology 2 domain fold (beta-sheet core with flanking alpha-helices).
• The erbB2 peptide adopts a beta-turn conformation, a rare binding mode for SH2 domains, suggesting an alternative ligand recognition mechanism.

Conclusions:

• The hGrb7-SH2 domain binds its natural ligand, erbB2 peptide, in an unusual beta-turn conformation.
• A four-residue insertion influences the SH2 domain/peptide complex structure.
• Characterization of binding specificity residues provides insights into potential functional consequences of mutations.