title: Structural basis of high-affinity nuclear localization signal interactions with importin-α.
abstract: Classical nuclear localization signals (cNLSs), comprising one (monopartite cNLSs) or two clusters of basic residues connected by a 10-12 residue linker (bipartite cNLSs), are recognized by the nuclear import factor importin-α. The cNLSs bind along a concave groove on importin-α; however, specificity determinants of cNLSs remain poorly understood. We present a structural and interaction analysis study of importin-α binding to both designed and naturally occurring high-affinity cNLS-like sequences; the peptide inhibitors Bimax1 and Bimax2, and cNLS peptides of cap-binding protein 80. Our data suggest that cNLSs and cNLS-like sequences can achieve high affinity through maximizing interactions at the importin-α minor site, and by taking advantage of multiple linker region interactions. Our study defines an extended set of binding cavities on the importin-α surface, and also expands on recent observations that longer linker sequences are allowed, and that long-range electrostatic complementarity can contribute to cNLS-binding affinity. Altogether, our study explains the molecular and structural basis of the results of a number of recent studies, including systematic mutagenesis and peptide library approaches, and provides an improved level of understanding on the specificity determinants of a cNLS. Our results have implications for identifying cNLSs in novel proteins.
authors.affiliation: School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD, 4072, Australia.
authors.forename: Mary
authors.initials: M
authors.lastname: Marfori
authors.forename: Thierry G
authors.initials: TG
authors.lastname: Lonhienne
authors.forename: Jade K
authors.initials: JK
authors.lastname: Forwood
authors.forename: Bostjan
authors.initials: B
authors.lastname: Kobe
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D039502:Nuclear Cap-Binding Protein Complex / Q000737:chemistry / Q000378:metabolism; D019913:Nuclear Localization Signals / Q000737:chemistry* / Q000502:physiology*; D015398:Signal Transduction; D028901:alpha Karyopherins / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D039502:Nuclear Cap-Binding Protein Complex; D019913:Nuclear Localization Signals; D028901:alpha Karyopherins