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PDBsum entry 1pv7
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Transport protein
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PDB id
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1pv7
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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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Structure and mechanism of the lactose permease of escherichia coli.
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Authors
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J.Abramson,
I.Smirnova,
V.Kasho,
G.Verner,
H.R.Kaback,
S.Iwata.
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Ref.
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Science, 2003,
301,
610-615.
[DOI no: ]
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PubMed id
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Abstract
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Membrane transport proteins that transduce free energy stored in electrochemical
ion gradients into a concentration gradient are a major class of membrane
proteins. We report the crystal structure at 3.5 angstroms of the Escherichia
coli lactose permease, an intensively studied member of the major facilitator
superfamily of transporters. The molecule is composed of N- and C-terminal
domains, each with six transmembrane helices, symmetrically positioned within
the permease. A large internal hydrophilic cavity open to the cytoplasmic side
represents the inward-facing conformation of the transporter. The structure with
a bound lactose homolog,
beta-D-galactopyranosyl-1-thio-beta-D-galactopyranoside, reveals the
sugar-binding site in the cavity, and residues that play major roles in
substrate recognition and proton translocation are identified. We propose a
possible mechanism for lactose/proton symport (co-transport) consistent with
both the structure and a large body of experimental data.
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Figure 2.
Fig. 2. The internal hydrophilic cavity of LacY. The surface
model and electrostatic potential were calculated with the
program GRASP (38). The polar surfaces are colored blue
(positively charged) and red (negatively charged). The black
spheres denote TDG. (A) View parallel to the membrane. For
clarity, helices V and VIII have been removed. (B) View along
the membrane normal from the cytoplasmic side.
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Figure 4.
Fig. 4. Residues involved in proton translocation and coupling.
Hydrogen bonds are represented by dashed black lines.
Transmembrane helices in the N- and C-terminal domains are
colored blue and red, respectively. Color code for atoms is as
in Fig. 3. (A) Stereo view parallel to the membrane. (B) Stereo
view along the membrane normal from the cytoplasmic side.
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The above figures are
reprinted
by permission from the AAAs:
Science
(2003,
301,
610-615)
copyright 2003.
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