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PDBsum entry 1xvb
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Oxidoreductase
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PDB id
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1xvb
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Contents |
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510 a.a.
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388 a.a.
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166 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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Product bound structures of the soluble methane monooxygenase hydroxylase from methylococcus capsulatus (bath): protein motion in the alpha-Subunit.
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Authors
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M.H.Sazinsky,
S.J.Lippard.
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Ref.
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J Am Chem Soc, 2005,
127,
5814-5825.
[DOI no: ]
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PubMed id
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Abstract
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The soluble methane monooxygenase hydroxylase (MMOH) alpha-subunit contains a
series of cavities that delineate the route of substrate entrance to and product
egress from the buried carboxylate-bridged diiron center. The presence of
discrete cavities is a major structural difference between MMOH, which can
hydroxylate methane, and toluene/o-xylene monooxygenase hydroxylase (ToMOH),
which cannot. To understand better the functions of the cavities and to
investigate how an enzyme designed for methane hydroxylation can also
accommodate larger substrates such as octane, methylcubane, and
trans-1-methyl-2-phenylcyclopropane, MMOH crystals were soaked with an
assortment of different alcohols and their X-ray structures were solved to
1.8-2.4 A resolution. The product analogues localize to cavities 1-3 and
delineate a path of product exit and/or substrate entrance from the active site
to the surface of the protein. The binding of the alcohols to a position
bridging the two iron atoms in cavity 1 extends and validates previous
crystallographic, spectroscopic, and computational work indicating this site to
be where substrates are hydroxylated and products form. The presence of these
alcohols induces perturbations in the amino acid side-chain gates linking pairs
of cavities, allowing for the formation of a channel similar to one observed in
ToMOH. Upon binding of 6-bromohexan-1-ol, the pi helix formed by residues
202-211 in helix E of the alpha-subunit is extended through residue 216,
changing the orientations of several amino acid residues in the active site
cavity. This remarkable secondary structure rearrangement in the four-helix
bundle has several mechanistic implications for substrate accommodation and the
function of the effector protein, MMOB.
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