title: Structural basis for substrate recognition and dissociation by human transportin 1.
abstract: Transportin 1 (Trn1) is a transport receptor that transports substrates from the cytoplasm to the nucleus through nuclear pore complexes by recognizing nuclear localization signals (NLSs). Here we describe four crystal structures of human Trn1 in a substrate-free form as well as in the complex with three NLSs (hnRNP D, JKTBP, and TAP, respectively). Our data have revealed that (1) Trn1 has two sites for binding NLSs, one with high affinity (site A) and one with low affinity (site B), and NLS interaction at site B controls overall binding affinity for Trn1; (2) Trn1 recognizes the NLSs at site A followed by conformational change at site B to interact with the NLSs; and (3) a long flexible loop, characteristic of Trn1, interacts with site B, thereby displacing transport substrate in the nucleus. These studies provide deep understanding of substrate recognition and dissociation by Trn1 in import pathways.
authors.affiliation: Field of Supramolecular Biology, International Graduate School of Arts and Sciences, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Imasaki
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Shimizu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hashimoto
authors.forename: Yuji
authors.initials: Y
authors.lastname: Hidaka
authors.forename: Shingo
authors.initials: S
authors.lastname: Kose
authors.forename: Naoko
authors.initials: N
authors.lastname: Imamoto
authors.forename: Michiyuki
authors.initials: M
authors.lastname: Yamada
authors.forename: Mamoru
authors.initials: M
authors.lastname: Sato
mesh_terms: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D034502:Heterogeneous-Nuclear Ribonucleoprotein D / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D019913:Nuclear Localization Signals / Q000235:genetics; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012261:Ribonucleoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013379:Substrate Specificity; D028961:beta Karyopherins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; C111986:HNRPDL protein, human; D034502:Heterogeneous-Nuclear Ribonucleoprotein D; D019913:Nuclear Localization Signals; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins; C073119:TAP1 protein, human; C108121:TNPO1 protein, human; D028961:beta Karyopherins