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PDBsum entry 1b3m
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Oxidoreductase
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PDB id
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1b3m
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References listed in PDB file
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Key reference
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Title
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Monomeric sarcosine oxidase: structure of a covalently flavinylated amine oxidizing enzyme.
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Authors
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P.Trickey,
M.A.Wagner,
M.S.Jorns,
F.S.Mathews.
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Ref.
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Structure Fold Des, 1999,
7,
331-345.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: Monomeric sarcosine oxidases (MSOXs) are among the simplest members
of a recently recognized family of eukaryotic and prokaryotic enzymes that
catalyze similar oxidative reactions with various secondary or tertiary amino
acids and contain covalently bound flavins. Other members of this family include
heterotetrameric sarcosine oxidase, N-methyltryptophan oxidase and pipecolate
oxidase. Mammalian sarcosine dehydrogenase and dimethylglycine dehydrogenase may
be more distantly related family members. RESULTS: The X-ray crystal structure
of MSOX from Bacillus sp. B-0618, expressed in Escherichia coli, has been solved
at 2.0 A resolution by multiwavelength anomalous dispersion (MAD) from crystals
of the selenomethionine-substituted enzyme. Fourteen selenium sites, belonging
to two MSOX molecules in the asymmetric unit, were used for MAD phasing and to
define the local twofold symmetry axis for electron-density averaging. The
structures of the native enzyme and of two enzyme-inhibitor complexes were also
determined. CONCLUSIONS: MSOX is a two-domain protein with an overall topology
most similar to that of D-amino acid oxidase, with which it shares 14% sequence
identity. The flavin ring is located in a very basic environment, making contact
with sidechains of arginine, lysine, histidine and the N-terminal end of a helix
dipole. The flavin is covalently attached through an 8alpha-S-cysteinyl linkage
to Cys315 of the catalytic domain. Covalent attachment is probably
self-catalyzed through interactions with the positive sidechains and the helix
dipole. Substrate binding is probably stabilized by hydrogen bonds between the
substrate carboxylate and two basic sidechains, Arg52 and Lys348, located above
the re face of the flavin ring.
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Figure 7.
Figure 7. Proposed mechanism for covalent flavinylation in
MSOX (Scheme III).
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The above figure is
reprinted
by permission from Cell Press:
Structure Fold Des
(1999,
7,
331-345)
copyright 1999.
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