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PDBsum entry 1q1e
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Transport protein
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PDB id
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1q1e
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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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A tweezers-Like motion of the ATP-Binding cassette dimer in an abc transport cycle.
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Authors
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J.Chen,
G.Lu,
J.Lin,
A.L.Davidson,
F.A.Quiocho.
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Ref.
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Mol Cell, 2003,
12,
651-661.
[DOI no: ]
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PubMed id
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Abstract
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The ATPase components of ATP binding cassette (ABC) transporters power the
transporters by binding and hydrolyzing ATP. Major conformational changes of an
ATPase are revealed by crystal structures of MalK, the ATPase subunit of the
maltose transporter from Escherichia coli, in three different dimeric
configurations. While other nucleotide binding domains or subunits display low
affinity for each other in the absence of the transmembrane segments, the MalK
dimer is stabilized through interactions of the additional C-terminal domains.
In the two nucleotide-free structures, the N-terminal nucleotide binding domains
are separated to differing degrees, and the dimer is maintained through contacts
of the C-terminal regulatory domains. In the ATP-bound form, the nucleotide
binding domains make contact and two ATPs lie buried along the dimer interface.
The two nucleotide binding domains of the dimer open and close like a pair of
tweezers, suggesting a regulatory mechanism for ATPase activity that may be
tightly coupled to translocation.
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Figure 4.
Figure 4. Closed, Semi-Open, and Open Structures of MalK
Homodimer with Superimposed RDsThe distances between two H89
residues in a homodimer are indicated.(A) Superimposed closed
form with bound ATP (yellow) and semi-open form without bound
ATP (blue). The excellent overlap of the RDs is evident by the
green color resulting from the combination of yellow and blue
colors.(B) Overlay of the semi-open (blue) and the open (red)
nucleotide-free structures.
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Figure 5.
Figure 5. A Model of the Interaction between the EAA Loops
of MalF and MalG Transmembrane Proteins and the Q Loop of
MalK(A) Model of the docking of the L loop of BtuC to the Q loop
of MalK. To obtain this model, the NBD of MalK from the
ATP-bound structure was aligned with the NBD of BtuCD. Color
codes: cyan, the BtuC L loop; blue, the Q loop of MalK; red and
purple, the Walker A motif of one subunit and the LSGGQ motif of
the other subunit, respectively. ATP is shown in
ball-and-stick.(B) Predicted helix-loop-helix motif of the EAA
loops of MalF and MalG. The L loop in the crystal structure of
BtuCD, which displays a helix-loop-helix configuration (Locher
et al., 2002), is the equivalent of the EAA loops.
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The above figures are
reprinted
by permission from Cell Press:
Mol Cell
(2003,
12,
651-661)
copyright 2003.
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