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PDBsum entry 1o6p
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Nuclear transport
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PDB id
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1o6p
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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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Glfg and fxfg nucleoporins bind to overlapping sites on importin-Beta.
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Authors
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R.Bayliss,
T.Littlewood,
L.A.Strawn,
S.R.Wente,
M.Stewart.
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Ref.
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J Biol Chem, 2002,
277,
50597-50606.
[DOI no: ]
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PubMed id
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Abstract
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The interaction between nuclear pore proteins (nucleoporins) and transport
factors is crucial for the translocation of macromolecules through nuclear
pores. Many nucleoporins contain FG sequence repeats, and previous studies have
demonstrated interactions between repeats containing FxFG or GLFG cores and
transport factors. The crystal structure of residues 1-442 of importin-beta
bound to a GLFG peptide indicates that this repeat core binds to the same
primary site as FxFG cores. Importin-beta-I178D shows reduced binding to both
FxFG and GLFG repeats, consistent with both binding to an overlapping site in
the hydrophobic groove between the A-helices of HEAT repeats 5 and 6. Moreover,
FxFG repeats can displace importin-beta or its S. cerevisiae homologue, Kap95,
bound to GLFG repeats. Addition of soluble GLFG repeats decreases the rate of
nuclear protein import in digitonin-permeabilized HeLa cells, indicating that
this interaction has a role in the translocation of carrier-cargo complexes
through nuclear pores. The binding of GLFG and FxFG repeats to overlapping sites
on importin-beta indicates that functional differences between different repeats
probably arise from differences in their spatial organization.
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Figure 1.
Fig. 1. Binding of GLFG and FxFG repeats to Ib442.
Annealed omit F[o]  F[c] maps
contoured at 2.5  at the
primary GLFG binding site (A) (site 1, see C) and the primary
FxFG binding site (B). C, the GLFG peptide showed difference
density located at two sites on Ib442. Site 1 (black) was
located between the A-helices of HEAT repeats 5 and 6 and was
also the primary site at which FxFG cores bound, whereas site 2
(red) was located at a contact between two Ib442 chains in the
crystal and was thought to be a crystallization artifact.
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Figure 2.
Fig. 2. Details of the interaction between GLFG and FxFG
cores and Ib442. Stereo views of GLFG (A, black) and FxFG (B,
red) cores show that each binds in the hydrophobic pocket
(yellow) formed between HEAT repeats 5 (light green) and 6
(light blue) by the side chains of Leu174, Thr175, Ile^178,
Glu214, Phe^217, and Ile^218. In addition to the hydrophobic
interaction, putative H-bonds are formed between the main chain
and Glu214. Thr175 forms a H-bond to the FxFG core but not to
the GLFG core. Surface views (D and E) illustrate the intimacy
of the contact between the repeat cores and Ib442. In contrast,
the contact between the GLFG peptide at site 2 involved a pocket
formed by two Ib442 chains (green and orange in C and F) and
neither Ib442 chain alone buried a significant amount of the
core, consistent with site 2 representing a crystallization
artifact and site 1 representing the true GLFG binding site. G,
although the conformation of GLFG and FxFG cores bound to Ib442
was different, they had a similar outline.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2002,
277,
50597-50606)
copyright 2002.
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