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PDBsum entry 1lsv
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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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Structure-Based mechanism of o2 sensing and ligand discrimination by the fixl heme domain of bradyrhizobium japonicum.
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Authors
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B.Hao,
C.Isaza,
J.Arndt,
M.Soltis,
M.K.Chan.
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Ref.
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Biochemistry, 2002,
41,
12952-12958.
[DOI no: ]
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PubMed id
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Abstract
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Structures of the Bradyrhizobium japonicum FixL heme domain have been determined
in the absence and presence of specific ligands to elucidate the detailed
features of its O2 sensing mechanism. The putative roles of spin-state and
steric hindrance were evaluated by the structure determination of ferrous
CO-bound BjFixLH and correlating its features with other ligand-bound
structures. As found for NO-BjFixLH, no protein conformational change was
observed in CO-BjFixLH, suggesting a more complicated mechanism than solely spin
state or ligand sterics. To evaluate the role of oxidation state, the structure
of the ferrous deoxy-BjFixLH was determined. The structure of deoxy-BjFixLH was
found to be virtually identical to the structure of the ferric met-BjFixLH. The
role of hydrogen bonding of substrates to a heme-pocket water was evaluated by
determining the structure of BjFixLH bound to 1-methyl-imidazole that cannot
form a hydrogen bond with this water. In this case, the heme-mediated
conformational change was observed, limiting the potential importance of this
interaction. Finally, the structure of cyanomet-BjFixLH was revisited to rule
out concerns regarding the partial occupancy of the cyanide ligand in a previous
structure. In the revised structure, Arg 220 was found to move into the heme
pocket to form a hydrogen bond to the bound cyanide ligand. The implications of
these results on FixL's sensing mechanism are discussed.
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