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PDBsum entry 1q1t
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Protein transport
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PDB id
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1q1t
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Role of flanking sequences and phosphorylation in the recognition of the simian-Virus-40 large t-Antigen nuclear localization sequences by importin-Alpha.
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Authors
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M.R.Fontes,
T.Teh,
G.Toth,
A.John,
I.Pavo,
D.A.Jans,
B.Kobe.
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Ref.
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Biochem J, 2003,
375,
339-349.
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PubMed id
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Abstract
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The nuclear import of simian-virus-40 large T-antigen (tumour antigen) is
enhanced via phosphorylation by the protein kinase CK2 at Ser112 in the vicinity
of the NLS (nuclear localization sequence). To determine the structural basis of
the effect of the sequences flanking the basic cluster KKKRK, and the effect of
phosphorylation on the recognition of the NLS by the nuclear import factor
importin-alpha (Impalpha), we co-crystallized non-autoinhibited Impalpha with
peptides corresponding to the phosphorylated and non-phosphorylated forms of the
NLS, and determined the crystal structures of the complexes. The structures show
that the amino acids N-terminally flanking the basic cluster make specific
contacts with the receptor that are distinct from the interactions between
bipartite NLSs and Impalpha. We confirm the important role of flanking sequences
using binding assays. Unexpectedly, the regions of the peptides containing the
phosphorylation site do not make specific contacts with the receptor. Binding
assays confirm that phosphorylation does not increase the affinity of the
T-antigen NLS to Impalpha. We conclude that the sequences flanking the basic
clusters in NLSs play a crucial role in nuclear import by modulating the
recognition of the NLS by Impalpha, whereas phosphorylation of the T-antigen
enhances nuclear import by a mechanism that does not involve a direct
interaction of the phosphorylated residue with Impalpha.
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Secondary reference #1
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Title
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Structural basis of recognition of monopartite and bipartite nuclear localization sequences by mammalian importin-Alpha.
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Authors
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M.R.Fontes,
T.Teh,
B.Kobe.
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Ref.
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J Mol Biol, 2000,
297,
1183-1194.
[DOI no: ]
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PubMed id
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Figure 2.
Figure 2. (a) Structure of the Impa(70-529)-SV40 NLS
complex. Importin-a is shown as a ribbon diagram (lavender;
drawn with program RIBBONS [Carson 1997]). The superhelical axis
of the repetitive part of the molecule is approximately
horizontal. The two SV40 NLS peptides are shown in a
ball-and-stick representation; the peptide bound to the major
site is colored yellow, and the peptide bound to the minor site
is colored orange. (b) Structure of Impa(70-529)-nucleoplasmin
NLS complex, shown as in (a). The nucleoplasmin NLS peptide is
colored cyan.
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Figure 4.
Figure 4. Schematic diagram of the interactions of NLS
peptides with importin-a. The NLS backbone is shown as a black
line, with the side-chains shown as perpendicular lines
radiating from it. Individual Arm repeats of importin-a are
separated by tilted lines. Some importin-a side-chains
interacting with the NLS peptides are indicated: the invariant
asparagine residues in magenta, the invariant tryptophan
residues in green, and some nearby negatively charged residues
are shown in red. Y277 and R315 that interrupt the regular
asparagine and tryptophan array are also shown.
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The above figures are
reproduced from the cited reference
with permission from Elsevier
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