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PDBsum entry 1ksf
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Hydrolase, ligand binding protein
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PDB id
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1ksf
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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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Crystal structure of clpa, An hsp100 chaperone and regulator of clpap protease.
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Authors
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F.Guo,
M.R.Maurizi,
L.Esser,
D.Xia.
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Ref.
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J Biol Chem, 2002,
277,
46743-46752.
[DOI no: ]
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PubMed id
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Abstract
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Escherichia coli ClpA, an Hsp100/Clp chaperone and an integral component of the
ATP-dependent ClpAP protease, participates in regulatory protein degradation and
the dissolution and degradation of protein aggregates. The crystal structure of
the ClpA subunit reveals an N-terminal domain with pseudo-twofold symmetry and
two AAA(+) modules (D1 and D2) each consisting of a large and a small sub-domain
with ADP bound in the sub-domain junction. The N-terminal domain interacts with
the D1 domain in a manner similar to adaptor-binding domains of other AAA(+)
proteins. D1 and D2 are connected head-to-tail consistent with a cooperative and
vectorial translocation of protein substrates. In a planar hexamer model of
ClpA, built by assembling ClpA D1 and D2 into homohexameric rings of known
structures of AAA(+) modules, the differences in D1-D1 and D2-D2 interfaces
correlate with their respective contributions to hexamer stability and ATPase
activity.
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Figure 5.
Fig. 5. Hexameric model of ClpA. Electrostatic potential
surface of the modeled planar ClpA hexagon as rendered in GRASP,
with negative potential in red, positive in blue, and neutral in
white. a, the hexagonal ring is viewed along the 6-fold axis
with the D1 domains facing out. The hexagon has a crenated edge
and maximum diameter of 170 Å. The larger crenations are
made by the six N-domains, which are attached to the outer edge
of the D1 domains; the smaller crenations are formed by
extensions of the D2-small domains. b, the D2 side is facing
out, showing the wide opening of the central cavity (red) and
residues forming part of the ClpP loop (yellow). c, side view of
the modeled ClpA hexagonal ring. The height is about 87 Å.
The six subunits are shown in different colors. D1 and D2 from
the same ClpA subunit are tilted with respect to the ring axis
and make little contact with each other. Each domain makes
extensive contacts with both D1 and D2 of a neighboring subunit.
d, cross section through the center and parallel to the 6-fold
axis of the modeled ClpA hexagonal ring. The surface of the
central cavity is colored to show the three negatively charged
belts (red) and the hydrophobic surfaces surrounding the
channels (gray). The borders of the cavity are outlined in
black. The two constrictions and the two compartments are as
labeled. The positions for the three remaining ClpP loop are
indicated in yellow.
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Figure 6.
Fig. 6. A hypothetical model describing transitions of
ClpA subunits in solution to form a spiral in crystal in the
presence of ADP and to assemble into a planar hexamer in
solution in the presence of ATP. ClpA subunits are postulated to
undergo an open and a closed conformation by rotating D2 with
respect to D1 via the hinge between two domains.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2002,
277,
46743-46752)
copyright 2002.
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