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PDBsum entry 2d2c
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Photosynthesis
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PDB id
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2d2c
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Contents |
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202 a.a.
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137 a.a.
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286 a.a.
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168 a.a.
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32 a.a.
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35 a.a.
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27 a.a.
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27 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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Intraprotein transfer of the quinone analogue inhibitor 2,5-Dibromo-3-Methyl-6-Isopropyl-P-Benzoquinone in the cytochrome b6f complex.
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Authors
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J.Yan,
G.Kurisu,
W.A.Cramer.
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Ref.
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Proc Natl Acad Sci U S A, 2006,
103,
69-74.
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PubMed id
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Abstract
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Details are presented of the structural analysis of the cytochrome b(6)f complex
from the thermophilic cyanobacterium, Mastigocladus laminosus, in the presence
of the electrochemically positive (p)-side quinone analogue inhibitor,
2,5-dibromo-3-methyl-6-isopropylbenzoquinone (DBMIB). One DBMIB binding site was
found. This site is peripheral to the quinone binding space defined by the
binding sites of other p-side inhibitors previously resolved in cytochrome
bc(1)/b(6)f complexes. This high-affinity site resides in a p-side interfacial
niche bounded by cytochrome f, subunit IV, and cytochrome b(6), is close (8 A)
to the p-side heme b, but distant (19 A) from the [2Fe-2S] cluster. No
significant electron density associated with the DBMIB was found elsewhere in
the structure. However, the site at which DBMIB can inhibit light-induced redox
turnover is within a few A of the [2Fe-2S] cluster, as shown by the absence of
inhibition in mutants of Synechococcus sp. PCC 7002 at iron sulfur
protein-Leu-111 near the cluster. The ability of a minimum amount of initially
oxidized DBMIB to inhibit turnover of WT complex after a second light flash
implies that there is a light-activated movement of DBMIB from the distal
peripheral site to an inhibitory site proximal to the [2Fe-2S] cluster. Together
with the necessary passage of quinone/quinol through the small Q(p) portal in
the complex, it is seen that transmembrane traffic of quinone-like molecules
through the core of cytochrome bc complexes can be labyrinthine.
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