Proton release due to manganese binding and oxidation in modified bacterial reaction centers

L. Kálmán, M. C. Thielges, J. C. Williams, James Paul Allen

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

The pH dependence of binding and oxidation of Mn2+ in highly oxidizing reaction centers with designed metal-binding sites was characterized by light-minus-dark optical difference spectroscopy and direct measurements of proton uptake/release. These mutants bind a Mn2+ ion that can efficiently transfer an electron to the oxidized bacteriochlorophyll dimer, as described earlier [Thielges et al. (2005) Biochemistry 44, 7389-7394]. The dissociation constant, KD, significantly increased with decreasing pH. The pH dependence of KD between pH 7 and pH 8 was consistent with the binding of Mn2+ being stabilized by the electrostatic release of two protons. The strong pH dependence of proton release upon Mn2+ binding, with a maximal release of 1.4 H+ per reaction center, was interpreted as being a result of a shift in the pKa values of the coordinating residues and possibly other nearby residues. A small amount of proton release associated with Mn2+ oxidation was observed upon illumination. These results show that functional metal-binding sites can be incorporated into proteins upon consideration of both the metal coordination and protonation states of the ligands.

Original languageEnglish
Pages (from-to)13266-13273
Number of pages8
JournalBiochemistry
Volume44
Issue number40
DOIs
Publication statusPublished - Oct 11 2005

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Manganese
Protons
Oxidation
Metals
Binding Sites
Bacteriochlorophylls
Biochemistry
Protonation
Dimers
Electrostatics
Lighting
Spectroscopy
Ions
Ligands
Static Electricity
Electrons
Spectrum Analysis
Light
Proteins

ASJC Scopus subject areas

  • Biochemistry

Cite this

Proton release due to manganese binding and oxidation in modified bacterial reaction centers. / Kálmán, L.; Thielges, M. C.; Williams, J. C.; Allen, James Paul.

In: Biochemistry, Vol. 44, No. 40, 11.10.2005, p. 13266-13273.

Research output: Contribution to journalArticle

Kálmán, L. ; Thielges, M. C. ; Williams, J. C. ; Allen, James Paul. / Proton release due to manganese binding and oxidation in modified bacterial reaction centers. In: Biochemistry. 2005 ; Vol. 44, No. 40. pp. 13266-13273.
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