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PDBsum entry 2z5o
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Transport protein/RNA binding protein
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PDB id
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2z5o
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References listed in PDB file
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Key reference
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Title
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Structural basis for substrate recognition and dissociation by human transportin 1.
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Authors
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T.Imasaki,
T.Shimizu,
H.Hashimoto,
Y.Hidaka,
S.Kose,
N.Imamoto,
M.Yamada,
M.Sato.
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Ref.
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Mol Cell, 2007,
28,
57-67.
[DOI no: ]
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PubMed id
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Abstract
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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.
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Figure 3.
Figure 3. NLS Recognition by Trn1
(A) Schematic
illustrations of Trn1 interactions with hnRNP D NLS (left) and
TAP NLS (right). Trn1-NLS contacts less than 3.8 Å are
shown. HEAT repeats 8–13 correspond to site A, and HEAT
repeats 14–18 to site B.
(B) Structures of hnRNP D NLS
(green), TAP NLS (blue), hnRNP A1 NLS (orange), and hnRNP M NLS
(purple) bound to Trn1. Two close-up views of the structures at
the right side and one close-up view at the left side show the
interactions with Trn1 at sites A and B, respectively.
Structures of hnRNP A1 NLS and hnRNP M NLS bound to an H8
loop-truncated Trn1 mutant were drawn with the refined
coordinates deposited in the Protein Data Bank (accession codes
2H4M and 2OT8).
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Figure 6.
Figure 6. Schematic Illustration of a Proposed Mechanism for
the Nuclear Import Pathway Mediated by Trn1
The Trn1
molecule is represented by the S-like cyan ribbon labeled with N
and C termini. NPC is the nuclear pore complex. Red and blue
ellipsoids on the NLS in transport substrate show the three
consensus residues (red ellipsoid) and one hydrophobic residue
(blue ellipsoid).
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The above figures are
reprinted
by permission from Cell Press:
Mol Cell
(2007,
28,
57-67)
copyright 2007.
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