title: Structure of a truncation mutant of the nuclear export factor CRM1 provides insights into the auto-inhibitory role of its C-terminal helix.
abstract: Chromosome region maintenance 1/exportin1/Xpo1 (CRM1) associates with the GTPase Ran to mediate the nuclear export of proteins bearing a leucine-rich nuclear export signal (NES). CRM1 consists of helical hairpin HEAT repeats and a C-terminal helical extension (C-extension) that inhibits the binding of NES-bearing cargos. We report the crystal structure and small-angle X-ray scattering analysis of a human CRM1 mutant with enhanced NES-binding activity due to deletion of the C-extension. We show that loss of the C-extension leads to a repositioning of CRM1's C-terminal repeats and to a more extended overall conformation. Normal mode analysis predicts reduced rigidity for the deletion mutant, consistent with an observed decrease in thermal stability. Point mutations that destabilize the C-extension shift CRM1 to the more extended conformation, reduce thermal stability, and enhance NES-binding activity. These findings suggest that an important mechanism by which the C-extension regulates CRM1's cargo-binding affinity is by modulating the conformation and flexibility of its HEAT repeats.
authors.affiliation: Université de Grenoble Alpes, Institut de Biologie Structurale, 38027 Grenoble, France.
authors.forename: Cyril
authors.initials: C
authors.lastname: Dian
authors.forename: Florent
authors.initials: F
authors.lastname: Bernaudat
authors.forename: Karla
authors.initials: K
authors.lastname: Langer
authors.forename: Mizar F
authors.initials: MF
authors.lastname: Oliva
authors.forename: Maarten
authors.initials: M
authors.lastname: Fornerod
authors.forename: Guy
authors.initials: G
authors.lastname: Schoehn
authors.forename: Christoph W
authors.initials: CW
authors.lastname: Müller
authors.forename: Carlo
authors.initials: C
authors.lastname: Petosa
mesh_terms: D018360:Crystallography, X-Ray; D006801:Humans; D028884:Karyopherins / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D016296:Mutagenesis; D017354:Point Mutation; D011485:Protein Binding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000235:genetics; D020449:Repetitive Sequences, Amino Acid; D053838:Scattering, Small Angle; D017384:Sequence Deletion; D000097606:Exportin 1 Protein
chemical_list: D028884:Karyopherins; D018160:Receptors, Cytoplasmic and Nuclear; D000097606:Exportin 1 Protein