title: Novel mode of ligand recognition by the Erbin PDZ domain.
abstract: Erbin contains a class I PDZ domain that binds to the C-terminal region of the receptor tyrosine kinase ErbB2, a class II ligand. The crystal structure of the human Erbin PDZ bound to the peptide EYLGLDVPV corresponding to the C-terminal residues 1247-1255 of human ErbB2 has been determined at 1.25-A resolution. The Erbin PDZ deviates from the canonical PDZ fold in that it contains a single alpha-helix. The isopropyl group of valine at position -2 of the ErbB2 peptide interacts with the Erbin Val(1351) and displaces the peptide backbone away from the alpha-helix, elucidating the molecular basis of class II ligand recognition by a class I PDZ domain. Strikingly, the phenolic ring of tyrosine -7 enters into a pocket formed by the extended beta 2-beta 3 loop of the Erbin PDZ. Phosphorylation of tyrosine -7 abolishes this interaction but does not affect the binding of the four C-terminal peptidic residues to PDZ, as revealed by the crystal structure of the Erbin PDZ complexed with a phosphotyrosine-containing ErbB2 peptide. Since phosphorylation of tyrosine -7 plays a critical role in ErbB2 function, the selective binding and sequestration of this residue in its unphosphorylated state by the Erbin PDZ provides a novel mechanism for regulation of the ErbB2-mediated signaling and oncogenicity.
authors.affiliation: Molecular Medicine Laboratory and Macromolecular Crystallography Unit, Division of Experimental Medicine, Harvard Institutes of Medicine, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Birrane
authors.forename: Judy
authors.initials: J
authors.lastname: Chung
authors.forename: John A A
authors.initials: JA
authors.lastname: Ladias
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D008024:Ligands; D018719:Erb-b2 Receptor Tyrosine Kinases; D011994:Recombinant Proteins; C413364:ERBIN protein, human