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Mn(II) binding by the anthracis repressor from Bacillus anthracis.

K Ilker Sen·Andrzej Sienkiewicz·John F Love·Johanna C vanderSpek·Piotr G Fajer·Timothy M Logan
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Abstract

The anthracis repressor (AntR) is a manganese-activated transcriptional regulator from Bacillus anthracis and is a member of the diphtheria toxin repressor (DtxR) family of proteins. In this paper, we characterize the Mn(II) binding and protein dimerization state using a combination of continuous wave (cw) and pulsed EPR methods. Equilibrium metal binding experiments showed that AntR binds 2 equivalents of Mn(II) with positive cooperativity and apparent dissociation constants of 210 and 16.6 microM. AntR showed sub-millisecond Mn(II) on-rates as measured using stopped-flow EPR. The kinetics of Mn(II) dissociation, measured by displacement with Zn(II), was biphasic with rate constants of 35.7 and 0.115 s(-1). Variable-temperature parallel and perpendicular mode cw EPR spectra showed no evidence of a spin-exchange interaction, suggesting that the two Mn(II) ions are not forming a binuclear cluster. Finally, size exclusion chromatography and double electron-electron resonance EPR demonstrated that AntR forms a dimer in the absence of Mn(II). These results provide insights into the metal activation of AntR and allow a comparison with related DtxR proteins.

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Bacillus anthracisBacterial ProteinsDNA-Binding ProteinsElectron Spin Resonance SpectroscopyKineticsManganeseProtein BindingProtein Structure, QuaternaryRepressor ProteinsJournal ArticleResearch Support, N.I.H., ExtramuralResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.

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K Ilker Sen, Andrzej Sienkiewicz, John F Love, Johanna C vanderSpek, Piotr G Fajer, Timothy M Logan. 2006-04-04. Mn(II) binding by the anthracis repressor from Bacillus anthracis.. https://doi.org/10.1021/bi052288g

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