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PDBsum entry 2f5c
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Transcription
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PDB id
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2f5c
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References listed in PDB file
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Key reference
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Title
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Structural basis for the metal-Selective activation of the manganese transport regulator of bacillus subtilis.
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Authors
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J.I.Kliegman,
S.L.Griner,
J.D.Helmann,
R.G.Brennan,
A.Glasfeld.
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Ref.
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Biochemistry, 2006,
45,
3493-3505.
[DOI no: ]
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PubMed id
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Abstract
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The manganese transport regulator (MntR) of Bacillus subtilis is activated by
Mn(2+) to repress transcription of genes encoding transporters involved in the
uptake of manganese. MntR is also strongly activated by cadmium, both in vivo
and in vitro, but it is poorly activated by other metal cations, including
calcium and zinc. The previously published MntR.Mn(2+) structure revealed a
binuclear complex of manganese ions with a metal-metal separation of 3.3 A
(herein designated the AB conformer). Analysis of four additional crystal forms
of MntR.Mn(2+) reveals that the AB conformer is only observed in monoclinic
crystals at 100 K, suggesting that this conformation may be stabilized by
crystal packing forces. In contrast, monoclinic crystals analyzed at room
temperature (at either pH 6.5 or pH 8.5), and a second hexagonal crystal form
(analyzed at 100 K), all reveal the shift of one manganese ion by 2.5 A, thereby
leading to a newly identified conformation (the AC conformer) with an
internuclear distance of 4.4 A. Significantly, the cadmium and calcium complexes
of MntR also contain binuclear complexes with a 4.4 A internuclear separation.
In contrast, the zinc complex of MntR contains only one metal ion per subunit,
in the A site. Isothermal titration calorimetry confirms the stoichiometry of
Mn(2+), Cd(2+), and Zn(2+) binding to MntR. We propose that the specificity of
MntR activation is tied to productive binding of metal ions at two sites; the A
site appears to act as a selectivity filter, determining whether the B or C site
will be occupied and thereby fully activate MntR.
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