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 language | English |
|---|---|
| Pages (from-to) | 13266-13273 |
| Number of pages | 8 |
| Journal | Biochemistry |
| Volume | 44 |
| Issue number | 40 |
| DOIs | |
| Publication status | Published - Oct 11 2005 |
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ASJC Scopus subject areas
- Biochemistry
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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 journal › Article
}
TY - JOUR
T1 - Proton release due to manganese binding and oxidation in modified bacterial reaction centers
AU - Kálmán, L.
AU - Thielges, M. C.
AU - Williams, J. C.
AU - Allen, James Paul
PY - 2005/10/11
Y1 - 2005/10/11
N2 - 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.
AB - 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.
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U2 - 10.1021/bi051149w
DO - 10.1021/bi051149w
M3 - Article
VL - 44
SP - 13266
EP - 13273
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 40
ER -