title: Differences between the interaction of beta-catenin with non-phosphorylated and single-mimicked phosphorylated 20-amino acid residue repeats of the APC protein.
abstract: The tumour suppressor protein adenomatous polyposis coli (APC) regulates the level and the intracellular localisation of the proto-oncoprotein beta-catenin. There are indications that a region comprising seven homologous 20-amino acid residue repeats within the APC protein is responsible for the interaction with beta-catenin and that the phosphorylation of conserved serine residues within these repeats increases the affinity for beta-catenin. We used biophysical methods to analyse the beta-catenin binding of single repeats or repeat combinations as non-phosphorylated or phosphorylated recombinant proteins. The non-phosphorylated repeats showed similar affinities, no matter whether they were tested as single recombinant repeats or in combination with neighbouring repeats. This result makes a cooperative influence between the repetitive motifs unlikely. The phosphorylation of the APC protein was mimicked by specific serine/aspartate mutations, which align to serine residues in the cytoplasmic beta-catenin binding domain of E-cadherin. Remarkably, the mimicked phosphorylation of a serine, which is not involved in beta-catenin interaction in the E-cadherin/beta-catenin complex, led to a significant increase in the APC affinity for beta-catenin. These results indicate structural differences between the E-cadherin/beta-catenin and the APC/beta-catenin complexes and provide quantitative evidence for the importance of the APC phosphorylation for its interaction with beta-catenin.
authors.affiliation: Max-Planck-Institut für molekulare Physiologie, Otto-Hahn-Strasse 11, D-44227 Dortmund, Germany.
authors.forename: Lara
authors.initials: L
authors.lastname: Tickenbrock
authors.forename: Katja
authors.initials: K
authors.lastname: Kössmeier
authors.forename: Holger
authors.initials: H
authors.lastname: Rehmann
authors.forename: Christian
authors.initials: C
authors.lastname: Herrmann
authors.forename: Oliver
authors.initials: O
authors.lastname: Müller
mesh_terms: D011125:Adenomatous Polyposis Coli / Q000378:metabolism*; D025601:Adenomatous Polyposis Coli Protein / Q000378:metabolism*; D001224:Aspartic Acid / Q000235:genetics; D015820:Cadherins / Q000737:chemistry; D002151:Calorimetry; D003593:Cytoplasm; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D018716:Molecular Mimicry; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000378:metabolism*; D012694:Serine / Q000235:genetics; D013816:Thermodynamics; D015534:Trans-Activators / Q000378:metabolism*; D051176:beta Catenin
chemical_list: D025601:Adenomatous Polyposis Coli Protein; C495270:CTNNB1 protein, human; D015820:Cadherins; D003598:Cytoskeletal Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D051176:beta Catenin; D001224:Aspartic Acid; D012694:Serine; D005982:Glutathione Transferase