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PDBsum entry 6tqw
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Oxidoreductase
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PDB id
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6tqw
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References listed in PDB file
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Key reference
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Title
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The bacillus anthracis class ib ribonucleotide reductase subunit nrdf intrinsically selects manganese over iron.
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Authors
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K.Grāve,
J.J.Griese,
G.Berggren,
M.D.Bennett,
M.Högbom.
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Ref.
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J Biol Inorg Chem, 2020,
25,
571-582.
[DOI no: ]
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PubMed id
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Abstract
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Correct protein metallation in the complex mixture of the cell is a prerequisite
for metalloprotein function. While some metals, such as Cu, are commonly
chaperoned, specificity towards metals earlier in the Irving-Williams series is
achieved through other means, the determinants of which are poorly understood.
The dimetal carboxylate family of proteins provides an intriguing example, as
different proteins, while sharing a common fold and the same 4-carboxylate
2-histidine coordination sphere, are known to require either a Fe/Fe, Mn/Fe or
Mn/Mn cofactor for function. We previously showed that the R2lox proteins from
this family spontaneously assemble the heterodinuclear Mn/Fe cofactor. Here we
show that the class Ib ribonucleotide reductase R2 protein from Bacillus
anthracis spontaneously assembles a Mn/Mn cofactor in vitro, under both aerobic
and anoxic conditions, when the metal-free protein is subjected to incubation
with MnII and FeII in equal concentrations. This
observation provides an example of a protein scaffold intrinsically predisposed
to defy the Irving-Williams series and supports the assumption that the Mn/Mn
cofactor is the biologically relevant cofactor in vivo. Substitution of a second
coordination sphere residue changes the spontaneous metallation of the protein
to predominantly form a heterodinuclear Mn/Fe cofactor under aerobic conditions
and a Mn/Mn metal center under anoxic conditions. Together, the results describe
the intrinsic metal specificity of class Ib RNR and provide insight into control
mechanisms for protein metallation.
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