title: The coiled coil region (amino acids 129-250) of the tumor suppressor protein adenomatous polyposis coli (APC). Its structure and its interaction with chromosome maintenance region 1 (Crm-1).
abstract: The APC (adenomatous polyposis coli) tumor suppressor protein has many different intracellular functions including a nuclear export activity. Only little is known about the molecular architecture of the 2843-amino acid APC protein. Guided by secondary structure predictions we identified a fragment close to the N-terminal end, termed APC-(129-250), as a soluble and protease-resistant domain. We solved the crystal structure of APC-(129-250), which is monomeric and consists of three alpha-helices forming two separate antiparallel coiled coils. APC-(129-250) includes the nuclear export signal NES-(165-174) at the C-terminal end of the first helix. Surprisingly, the conserved hydrophobic amino acids of NES-(165-174) are buried in one of the coiled coils and are thus not accessible for interaction with other proteins. We demonstrate the direct interaction of APC-(129-250) with the nuclear export factor chromosome maintenance region 1 (Crm-1). This interaction is enhanced by the small GTPase Ran in its activated GTP-bound form and also by a double mutation in APC-(129-250), which deletes two amino acids forming two of the major interhelical interactions within the coiled coil. These observations hint to a regulatory mechanism of the APC nuclear export activity by NES masking.
authors.affiliation: Max-Planck-Institut für molekulare Physiologie, Abteilung Strukturelle Biologie, Otto-Hahn-Strasse 11, D-44227 Dortmund, Germany.
authors.forename: Lara
authors.initials: L
authors.lastname: Tickenbrock
authors.forename: Janina
authors.initials: J
authors.lastname: Cramer
authors.forename: Ingrid R
authors.initials: IR
authors.lastname: Vetter
authors.forename: Oliver
authors.initials: O
authors.lastname: Muller
mesh_terms: D025601:Adenomatous Polyposis Coli Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D002878:Chromosomes, Human, Pair 1; D003001:Cloning, Molecular; D015179:Colorectal Neoplasms / Q000235:genetics; D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017384:Sequence Deletion; D014357:Trypsin
chemical_list: D025601:Adenomatous Polyposis Coli Protein; D014357:Trypsin