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PDBsum entry 3fh6
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Transport protein
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PDB id
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3fh6
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Contents |
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316 a.a.
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254 a.a.
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371 a.a.
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References listed in PDB file
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Key reference
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Title
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Alternating access in maltose transporter mediated by rigid-Body rotations.
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Authors
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D.Khare,
M.L.Oldham,
C.Orelle,
A.L.Davidson,
J.Chen.
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Ref.
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Mol Cell, 2009,
33,
528-536.
[DOI no: ]
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PubMed id
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Note: In the PDB file this reference is
annotated as "TO BE PUBLISHED". The citation details given above have
been manually determined.
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Abstract
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ATP-binding cassette transporters couple ATP hydrolysis to substrate
translocation through an alternating access mechanism, but the nature of the
conformational changes in a transport cycle remains elusive. Previously we
reported the structure of the maltose transporter MalFGK(2) in an outward-facing
conformation in which the transmembrane (TM) helices outline a substrate-binding
pocket open toward the periplasmic surface and ATP is poised for hydrolysis
along the closed nucleotide-binding dimer interface. Here we report the
structure of the nucleotide-free maltose transporter in which the substrate
binding pocket is only accessible from the cytoplasm and the nucleotide-binding
interface is open. Comparison of the same transporter crystallized in two
different conformations reveals that alternating access involves rigid-body
rotations of the TM subdomains that are coupled to the closure and opening of
the nucleotide-binding domain interface. The comparison also reveals that point
mutations enabling binding protein-independent transport line dynamic interfaces
in the TM region.
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Figure 2.
Figure 2. Alternating Access in the Maltose Transporter
Ribbon diagram (left) and a 12 Å slab view (right) of the
maltose transporter in (A) the inward-facing, resting-state
conformation and (B) the outward-facing, catalytic intermediate
conformation (Oldham et al., 2007). The maltose and ATP are
shown in CPK and ball-and-stick models, respectively.
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Figure 4.
Figure 4. Conformational Changes in the MalK Subunits
(A
and B) Ribbon diagram of the MalK (A) open dimer in the
inward-facing structure and (B) closed dimer in the
outward-facing structure. The two NBDs are colored in green and
red, and the regulatory domains are colored in gray. The helical
subdomains are indicated and colored in light green or red. The
Walker A (WA) and the LSGGQ motifs are colored in blue and
yellow, respectively. ATP is shown in stick models.
(C)
Stereodiagram of MalK in the resting state. Using the regulatory
domains (gray) as the frame of reference, rotations of the two
NBDs (green and red) leading to the closed dimer are indicated.
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The above figures are
reprinted
from an Open Access publication published by Cell Press:
Mol Cell
(2009,
33,
528-536)
copyright 2009.
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