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PDBsum entry 1pyh
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Photosynthesis
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PDB id
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1pyh
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Contents |
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281 a.a.
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302 a.a.
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241 a.a.
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(+ 10 more)
26 a.a.
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(+ 9 more)
30 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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Crystal structure of the rc-Lh1 core complex from rhodopseudomonas palustris.
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Authors
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A.W.Roszak,
T.D.Howard,
J.Southall,
A.T.Gardiner,
C.J.Law,
N.W.Isaacs,
R.J.Cogdell.
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Ref.
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Science, 2003,
302,
1969-1972.
[DOI no: ]
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PubMed id
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Abstract
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The crystal structure at 4.8 angstrom resolution of the reaction center-light
harvesting 1 (RC-LH1) core complex from Rhodopseudomonas palustris shows the
reaction center surrounded by an oval LH1 complex that consists of 15 pairs of
transmembrane helical alpha- and beta-apoproteins and their coordinated
bacteriochlorophylls. Complete closure of the RC by the LH1 is prevented by a
single transmembrane helix, out of register with the array of inner LH1
alpha-apoproteins. This break, located next to the binding site in the reaction
center for the secondary electron acceptor ubiquinone (UQB), may provide a
portal through which UQB can transfer electrons to cytochrome b/c1.
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Figure 1.
Fig. 1. A representation of the major membrane proteins
involved in the light reactions of purple bacterial
photosynthesis. Photon energy (yellow arrows) captured by the
Bchla pigments (labeled B800 and B850 to indicate the
approximate wavelength in nanometers of maximal absorption) in
the antenna LH2 (purple) is passed to the LH1 Bchla (B880, red,
which also acts as a light-harvester), and then to a pair of
Bchla molecules (not shown) in the RC. Electron flow (red
arrows) occurs across the photosynthetic membrane from Bchla,
which is oxidized, to a primary electron acceptor, ubiquinone
(UQ[A], not shown), which is reduced. Subsequently, the electron
is transferred from UQ[A] to the secondary electron acceptor
ubiquinone (UQB, shown here as Q[B]). A second RC turnover
results in the complete reduction of UQ[B]^- to UQ[B]H[2]. The
fully reduced UQ[B]H[2] is replaced in the RC with an oxidized
ubiquinone (shown as Q) and passes its electrons to the next
redox component in the cyclic electron transport path, the
cytochrome b/c[1] complex (blue) (15). Electrons (e^-) are
returned to the RC through cytochrome c (Cyt c). A transmembrane
proton gradient is established and drives ATP synthase (orange),
producing ATP. ADP+Pi, adenosine diphosphate and inorganic
phosphate.
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Figure 3.
Fig. 3. Crystal packing of the RC-LH1 core complex (yellow)
viewed parallel to the membrane plane; all neighboring molecules
are colored blue.
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The above figures are
reprinted
by permission from the AAAs:
Science
(2003,
302,
1969-1972)
copyright 2003.
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