Direct binding of p130(Cas) to the guanine nucleotide exchange factor C3G.

p130(Cas) (Cas; crk-associated substrate) belongs to a new family of docking molecules. It contains one Src homology (SH) 3 domain in its amino-terminal region followed by a region containing binding motifs for SH2 and SH3 domains. To gain further insight into Cas signaling we used the SH3 domain of Cas ...
in a two-hybrid screen to search a human placenta library for binding partners. The screen confirmed a previous finding of its binding to the focal adhesion kinase (FAK) but also identified C3G, a guanine nucleotide exchange factor. We found direct interaction between Cas and C3G in vitro and in vivo. A series of analysis with C3G deletion mutants revealed a proline-rich Cas-binding site (Ala0-Pro1-Pro2-Lys3-Pro4-Pro5-Leu6-Pro7) located NH2-terminal to the previously characterized Crk binding motifs in C3G. Mutagenesis studies showed that Pro1, Lys3, and Pro4 within the ligand-binding site are critical for high affinity interaction. These results, combined with sequence alignments of proline-rich binding elements from proteins known for Cas binding, define the consensus sequence XXPXKPX which is recognized by the CasSH3 domain. Cas shows structural characteristics of a docking molecule and may serve to bring C3G to specific compartments within the cell.
Mesh Terms:
Amino Acid Sequence, Binding Sites, Consensus Sequence, Crk-Associated Substrate Protein, DNA Mutational Analysis, Guanine Nucleotide Exchange Factors, Humans, Molecular Sequence Data, Mutagenesis, Site-Directed, Phosphoproteins, Placenta, Proline, Protein Binding, Proteins, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-crk, Recombinant Fusion Proteins, Retinoblastoma-Like Protein p130, Sequence Alignment, Sequence Deletion, src Homology Domains
J. Biol. Chem.
Date: Oct. 02, 1998
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