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PDBsum entry 2fbz
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Oxidoreductase
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PDB id
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2fbz
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References listed in PDB file
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Key reference
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Title
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Nitrosyl-Heme structures of bacillus subtilis nitric oxide synthase have implications for understanding substrate oxidation.
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Authors
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K.Pant,
B.R.Crane.
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Ref.
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Biochemistry, 2006,
45,
2537-2544.
[DOI no: ]
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PubMed id
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Abstract
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The crystal structures of nitrosyl-heme complexes of a prokaryotic nitric oxide
synthase (NOS) from Bacillus subtilis (bsNOS) reveal changes in active-site
hydrogen bonding in the presence of the intermediate N(omega)-hydroxy-l-arginine
(NOHA) compared to the substrate l-arginine (l-Arg). Correlating with a
Val-to-Ile residue substitution in the bsNOS heme pocket, the Fe(II)-NO complex
with both l-Arg and NOHA is more bent than the Fe(II)-NO, l-Arg complex of
mammalian eNOS [Li, H., Raman, C. S., Martasek, P., Masters, B. S. S., and
Poulos, T. L. (2001) Biochemistry 40, 5399-5406]. Structures of the Fe(III)-NO
complex with NOHA show a nearly linear nitrosyl group, and in one subunit,
partial nitrosation of bound NOHA. In the Fe(II)-NO complexes, the protonated
NOHA N(omega) atom forms a short hydrogen bond with the heme-coordinated NO
nitrogen, but active-site water molecules are out of hydrogen bonding range with
the distal NO oxygen. In contrast, the l-Arg guanidinium interacts more weakly
and equally with both NO atoms, and an active-site water molecule hydrogen bonds
to the distal NO oxygen. This difference in hydrogen bonding to the nitrosyl
group by the two substrates indicates that interactions provided by NOHA may
preferentially stabilize an electrophilic peroxo-heme intermediate in the second
step of NOS catalysis.
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