Copper Binding Sites in the Manganese-Oxidizing Mnx Protein Complex Investigated by Electron Paramagnetic Resonance Spectroscopy

Lizhi Tao, Troy A. Stich, Shu Hao Liou, Alexandra V. Soldatova, David A. Delgadillo, Christine A. Romano, Thomas G. Spiro, David B. Goodin, Bradley Tebo, William H. Casey, R. David Britt

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Abstract

Manganese-oxide minerals (MnOx) are widely distributed over the Earth's surface, and their geochemical cycling is globally important. A multicopper oxidase (MCO) MnxG protein from marine Bacillus bacteria plays an essential role in producing MnOx minerals by oxidizing Mn2+(aq) at rates that are 3 to 5 orders of magnitude faster than abiotic rates. The MnxG protein is isolated as part of a multiprotein complex denoted as "Mnx" that includes accessory protein subunits MnxE and MnxF, with an estimated stoichiometry of MnxE3F3G and corresponding molecular weight of ?211 kDa. Herein, we report successful expression and isolation of the MCO MnxG protein without the E3F3 hexamer. This isolated MnxG shows activity for Mn2+(aq) oxidation to form manganese oxides. The complement of paramagnetic Cu(II) ions in the Mnx protein complex was examined by electron paramagnetic resonance (EPR) spectroscopy. Two distinct classes of type 2 Cu sites were detected. One class of Cu(II) site (denoted as T2Cu-A), located in the MnxG subunit, is identified by the magnetic parameters g? = 2.320 and A? = 510 MHz. The other class of Cu(II) sites (denoted as T2Cu-B) is characterized by g? = 2.210 and A? = 615 MHz and resides in the putative hexameric MnxE3F3 subunit. These different magnetic properties correlate with the differences in the reduction potentials of the respective Cu(II) centers. These studies provide new insights into the molecular mechanism of manganese biomineralization.

Original languageEnglish (US)
Pages (from-to)8868-8877
Number of pages10
JournalJournal of the American Chemical Society
Volume139
Issue number26
DOIs
StatePublished - Jul 5 2017

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Electron Spin Resonance Spectroscopy
Binding sites
Manganese
Paramagnetic resonance
Copper
Spectrum Analysis
Binding Sites
Oxide minerals
Spectroscopy
Manganese oxide
Proteins
Minerals
Oxidoreductases
Biomineralization
Multiprotein Complexes
Protein Subunits
Accessories
Bacilli
Stoichiometry
Bacillus

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Tao, L., Stich, T. A., Liou, S. H., Soldatova, A. V., Delgadillo, D. A., Romano, C. A., ... Britt, R. D. (2017). Copper Binding Sites in the Manganese-Oxidizing Mnx Protein Complex Investigated by Electron Paramagnetic Resonance Spectroscopy. Journal of the American Chemical Society, 139(26), 8868-8877. https://doi.org/10.1021/jacs.7b02277

Copper Binding Sites in the Manganese-Oxidizing Mnx Protein Complex Investigated by Electron Paramagnetic Resonance Spectroscopy. / Tao, Lizhi; Stich, Troy A.; Liou, Shu Hao; Soldatova, Alexandra V.; Delgadillo, David A.; Romano, Christine A.; Spiro, Thomas G.; Goodin, David B.; Tebo, Bradley; Casey, William H.; Britt, R. David.

In: Journal of the American Chemical Society, Vol. 139, No. 26, 05.07.2017, p. 8868-8877.

Research output: Contribution to journalArticle

Tao, L, Stich, TA, Liou, SH, Soldatova, AV, Delgadillo, DA, Romano, CA, Spiro, TG, Goodin, DB, Tebo, B, Casey, WH & Britt, RD 2017, 'Copper Binding Sites in the Manganese-Oxidizing Mnx Protein Complex Investigated by Electron Paramagnetic Resonance Spectroscopy', Journal of the American Chemical Society, vol. 139, no. 26, pp. 8868-8877. https://doi.org/10.1021/jacs.7b02277
Tao, Lizhi ; Stich, Troy A. ; Liou, Shu Hao ; Soldatova, Alexandra V. ; Delgadillo, David A. ; Romano, Christine A. ; Spiro, Thomas G. ; Goodin, David B. ; Tebo, Bradley ; Casey, William H. ; Britt, R. David. / Copper Binding Sites in the Manganese-Oxidizing Mnx Protein Complex Investigated by Electron Paramagnetic Resonance Spectroscopy. In: Journal of the American Chemical Society. 2017 ; Vol. 139, No. 26. pp. 8868-8877.
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AU - Soldatova, Alexandra V.

AU - Delgadillo, David A.

AU - Romano, Christine A.

AU - Spiro, Thomas G.

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AU - Casey, William H.

AU - Britt, R. David

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AB - Manganese-oxide minerals (MnOx) are widely distributed over the Earth's surface, and their geochemical cycling is globally important. A multicopper oxidase (MCO) MnxG protein from marine Bacillus bacteria plays an essential role in producing MnOx minerals by oxidizing Mn2+(aq) at rates that are 3 to 5 orders of magnitude faster than abiotic rates. The MnxG protein is isolated as part of a multiprotein complex denoted as "Mnx" that includes accessory protein subunits MnxE and MnxF, with an estimated stoichiometry of MnxE3F3G and corresponding molecular weight of ?211 kDa. Herein, we report successful expression and isolation of the MCO MnxG protein without the E3F3 hexamer. This isolated MnxG shows activity for Mn2+(aq) oxidation to form manganese oxides. The complement of paramagnetic Cu(II) ions in the Mnx protein complex was examined by electron paramagnetic resonance (EPR) spectroscopy. Two distinct classes of type 2 Cu sites were detected. One class of Cu(II) site (denoted as T2Cu-A), located in the MnxG subunit, is identified by the magnetic parameters g? = 2.320 and A? = 510 MHz. The other class of Cu(II) sites (denoted as T2Cu-B) is characterized by g? = 2.210 and A? = 615 MHz and resides in the putative hexameric MnxE3F3 subunit. These different magnetic properties correlate with the differences in the reduction potentials of the respective Cu(II) centers. These studies provide new insights into the molecular mechanism of manganese biomineralization.

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