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PDBsum entry 1dii
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Oxidoreductase
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PDB id
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1dii
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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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Structures of the flavocytochrome p-Cresol methylhydroxylase and its enzyme-Substrate complex: gated substrate entry and proton relays support the proposed catalytic mechanism.
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Authors
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L.M.Cunane,
Z.W.Chen,
N.Shamala,
F.S.Mathews,
C.N.Cronin,
W.S.Mcintire.
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Ref.
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J Mol Biol, 2000,
295,
357-374.
[DOI no: ]
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PubMed id
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Abstract
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The degradation of the toxic phenol p-cresol by Pseudomonas bacteria occurs by
way of the protocatechuate metabolic pathway. The first enzyme in this pathway,
p-cresol methylhydroxylase (PCMH), is a flavocytochrome c. The enzyme first
catalyzes the oxidation of p-cresol to p-hydroxybenzyl alcohol, utilizing one
atom of oxygen derived from water, and yielding one molecule of reduced FAD. The
reducing electron equivalents are then passed one at a time from the flavin
cofactor to the heme cofactor by intramolecular electron transfer, and
subsequently to cytochrome oxidase within the periplasmic membrane via one or
more soluble electron carrier proteins. The product, p-hydroxybenzyl alcohol,
can also be oxidized by PCMH to yield p-hydroxybenzaldehyde. The fully refined
X-ray crystal structure of PCMH in the native state has been obtained at 2. 5 A
resolution on the basis of the gene sequence. The structure of the
enzyme-substrate complex has also been refined, at 2.75 A resolution, and
reveals significant conformational changes in the active site upon substrate
binding. The active site for substrate oxidation is deeply buried in the
interior of the PCMH molecule. A route for substrate access to the site has been
identified and is shown to be governed by a swinging-gate mechanism. Two
possible proton transfer pathways, that may assist in activating the substrate
for nucleophilic attack and in removal of protons generated during the reaction,
have been revealed. Hydrogen bonding interactions between the flavoprotein and
cytochrome subunits that stabilize the intramolecular complex and may contribute
to the electron transfer process have been identified.
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Figure 2.
Figure 2. Stereo view of the PCMH heterotetramer as a
ribbon drawing. The two flavoprotein subunits are in light and
dark green, and the two cytochrome subunits are in red and
yellow. The heme prosthetic groups are in red and the FAD groups
are in gold. The molecular 2-fold axis is horizontal. Figure
prepared using Ribbons [Carson 1997].
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Figure 11.
Figure 11. Flavin and heme arrangement in PCMH. The light
blue broken line indicates the most efficient electron transfer
pathway according to the computer program GREENPATH (see the
text). The green broken line represents the next most efficient
pathway, and the pink and dark blue lines show the third most
efficient pathways for the p-cresol bound and native enzymes,
respectively. See Table 3.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2000,
295,
357-374)
copyright 2000.
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Secondary reference #1
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Title
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Three-Dimensional structure of p-Cresol methylhydroxylase (flavocytochrome c) from pseudomonas putida at 3.0-A resolution.
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Authors
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F.S.Mathews,
Z.W.Chen,
H.D.Bellamy,
W.S.Mcintire.
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Ref.
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Biochemistry, 1991,
30,
238-247.
[DOI no: ]
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PubMed id
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