Reduction of the oxidized bacteriochlorophyll dimer in reaction centers by ferrocene is dependent upon the driving force
Abstract
The rates of electron transfer from ferrocene to the oxidized bacteriochlorophyll dimer, P, in reaction centers from the purple photosynthetic bacterium Rhodobacter sphaeroides, were measured for a series of mutants in which the P/P+ midpoint potentials range from 410 to 765 mV (Lin et al. Proc. Natl. Acad. Sci. USA 1994; 91: 10265-10269). The observed rate constant for each mutant was found to be linearly dependent upon the ferrocene concentration up to 50 μM. The electron transfer is described as a second order reaction with rate constants increasing from 1.5 to 35 × 106M-1.s-1 with increasing P/P+ midpoint potential. This dependence was tested for three additional mutants, each of which exhibits a pH dependence of the P/P+ midpoint potential due to an electrostatic interaction with an introduced carboxylic group (Williams et al. Biochemistry 2001; 40: 15403-15407). For these mutants, the pH dependence of the bimolecular rate constants followed a sigmoidal pattern that could be described with a Henderson-Hasselbalch equation, attributable to the change of the free energy difference for the reaction due to deprotonation of the introduced carboxylic side chains.
References
- , The Photosynthetic Reaction Center 2, eds.
J. Deisenhofer and J. R. Norris (Academic Press, San Diego, 1993) pp. 49–70. Crossref, Google Scholar - , Anoxygenic Photosynthetic Bacteria: Advances in Photosynthesis 2, eds.
R. E. Blankenship , M. T. Madigan and C. E. Bauer (Kluwer Academic Publishers, Dordrecht, The Netherlands, 1995) pp. 527–557. Google Scholar - Annu. Rev. Biochem. 61, 861 (1992), DOI: 10.1146/annurev.bi.61.070192.004241. Crossref, ISI, Google Scholar
- , Anoxygenic Photosynthetic Bacteria: Advances in Photosynthesis 2, eds.
R. E. Blankenship , M. T. Madigan and C. E. Bauer (Kluwer Academic Publishers, Dordrecht, The Netherlands, 1995) pp. 577–594. Google Scholar - Proc. Natl. Acad. Sci. U.S.A. 84, 6162 (1987), DOI: 10.1073/pnas.84.17.6162. Crossref, ISI, Google Scholar
- Biochemistry 30, 5352 (1991), DOI: 10.1021/bi00236a005. Crossref, ISI, Google Scholar
- Structure 2, 925 (1994), DOI: 10.1016/S0969-2126(94)00094-8. Crossref, ISI, Google Scholar
- Acta Crystallogr. D 51, 368 (1995), DOI: 10.1107/S0907444994013120. Crossref, ISI, Google Scholar
- Biochemistry 19, 3322 (1980), DOI: 10.1021/bi00555a034. Crossref, ISI, Google Scholar
- Biochemistry 32, 4515 (1993), DOI: 10.1021/bi00068a006. Crossref, ISI, Google Scholar
- Biochim. Biophys. Acta 1187, 177 (1994). Crossref, ISI, Google Scholar
- Biophys. J. 74, 3226 (1998), DOI: 10.1016/S0006-3495(98)78029-4. Crossref, ISI, Google Scholar
- Biochemistry 37, 14457 (1998), DOI: 10.1021/bi981139d. Crossref, ISI, Google Scholar
- Biochim. Biophys. Acta. 934, 329 (1988). Crossref, Google Scholar
- Biochemistry 33, 9237 (1994). Crossref, Google Scholar
- J. Am. Chem. Soc. 118, 9005 (1996), DOI: 10.1021/ja960056m. Crossref, ISI, Google Scholar
- Proc. Natl. Acad. Sci. U.S.A. 91, 10265 (1994), DOI: 10.1073/pnas.91.22.10265. Crossref, ISI, Google Scholar
- Biochemistry 40, 15403 (2001), DOI: 10.1021/bi011574z. Crossref, ISI, Google Scholar
- J. Phys. Chem. B 106, 7376 (2002), DOI: 10.1021/jp0257552. Crossref, Google Scholar
- Biochim. Biophys. Acta 1276, 171 (1996). Crossref, ISI, Google Scholar
- Photosynth. Res. 41, 115 (1994), DOI: 10.1007/BF02184151. Crossref, ISI, Google Scholar
- Biochemistry 33, 13517 (1994), DOI: 10.1021/bi00250a002. Crossref, ISI, Google Scholar
- Biochim. Biophys. Acta 811, 265 (1985). Crossref, ISI, Google Scholar
- J. Bioenerg. Biomemb. 27, 275 (1995), DOI: 10.1007/BF02110097. Crossref, Google Scholar
- Biochemistry 40, 8452 (2001), DOI: 10.1021/bi010222p. Crossref, ISI, Google Scholar
- Electrochim. Acta 29, 521 (1984), DOI: 10.1016/0013-4686(84)87103-0. Crossref, ISI, Google Scholar
- Biochemistry 42, 11016 (2003). Crossref, Google Scholar
- Biochemistry 45, 13869 (2006). Crossref, Google Scholar
- Biochemistry 44, 7389 (2005), DOI: 10.1021/bi050377n. Crossref, ISI, Google Scholar
-
N. N. Greenwood and P. Earnshow , Chemistry of the elements ( Pergamon Press , Oxford , 1984 ) . Google Scholar -
R. M. Garrels and C. L. Christ , Solutions, minerals and equilibria ( Harper & Row , New York , 1965 ) . Google Scholar - , The proterozoic biosphere, eds.
J. W. Schopf and C. Klein (Cambridge University Press, Cambridge, 1992) pp. 147–151. Google Scholar - J. Photochem. Photobiol. A 179, 79 (2005). Google Scholar
- Nature 362, 834 (1993), DOI: 10.1038/362834a0. Crossref, ISI, Google Scholar
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