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PDBsum entry 1amo
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Oxidoreductase
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PDB id
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1amo
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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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Three-Dimensional structure of NADPH-Cytochrome p450 reductase: prototype for fmn- And FAD-Containing enzymes.
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Authors
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M.Wang,
D.L.Roberts,
R.Paschke,
T.M.Shea,
B.S.Masters,
J.J.Kim.
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Ref.
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Proc Natl Acad Sci U S A, 1997,
94,
8411-8416.
[DOI no: ]
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PubMed id
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Abstract
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Microsomal NADPH-cytochrome P450 reductase (CPR) is one of only two mammalian
enzymes known to contain both FAD and FMN, the other being nitric-oxide
synthase. CPR is a membrane-bound protein and catalyzes electron transfer from
NADPH to all known microsomal cytochromes P450. The structure of rat liver CPR,
expressed in Escherichia coli and solubilized by limited trypsinolysis, has been
determined by x-ray crystallography at 2.6 A resolution. The molecule is
composed of four structural domains: (from the N- to C- termini) the FMN-binding
domain, the connecting domain, and the FAD- and NADPH-binding domains. The
FMN-binding domain is similar to the structure of flavodoxin, whereas the two
C-terminal dinucleotide-binding domains are similar to those of ferredoxin-NADP+
reductase (FNR). The connecting domain, situated between the FMN-binding and
FNR-like domains, is responsible for the relative orientation of the other
domains, ensuring the proper alignment of the two flavins necessary for
efficient electron transfer. The two flavin isoalloxazine rings are juxtaposed,
with the closest distance between them being about 4 A. The bowl-shaped surface
near the FMN-binding site is likely the docking site of cytochrome c and the
physiological redox partners, including cytochromes P450 and b5 and heme
oxygenase.
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Figure 1.
Fig. 1. Stereoview of the electron density in the vicinity of
the FAD and FMN of CPR. The 3|F[o]|  2|F[c]|
electron density map computed^ with 2.6 Å resolution data
is contoured at 1.2  level.
Residues within close contact of the flavin ring are labeled.
Four aromatic^ residues sandwich the flavin rings: Y178 and Y140
for FMN and^ Y456 and W677 for FAD.
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Figure 4.
Fig. 4. Stereoview of the cofactor arrangement in CPR and
multiple conformers for the bound NADP+. Electrons flow from
NADPH to FAD and then to FMN. The FMN and^ FAD are represented
by ball-and-stick, with the xylene portions of the isoalloxazine
rings oriented toward each other. The adenine^ portion of NADP+
binds in a single conformation (ball-and-stick) while the
nicotinamide^ (stick only) binds in multiple conformations. By
rotation about the P[N]---O---P[A] bond, the nicotinamide ring
could displace W677 at the re-side of the FAD ring, placing it
in the optimum orientation for hydride transfer from the NADPH
to the N5 position of the^ FAD cofactor.
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