Effects of mutations near the bacteriochlorophylls in reaction centers from rhodobacter sphaeroides

J. C. Williams, R. G. Alden, H. A. Murchison, J. M. Peloquin, N. W. Woodbury, James Paul Allen

Research output: Contribution to journalArticle

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Abstract

Mutations were made in four residues near the bacteriochlorophyll cofactors of the photosynthetic reaction center from Rhodobacter sphaeroides. These mutations, L131 Leu to His and M160 Leu to His, near the dimer bacteriochlorophylls, and M203 Gly to Asp and L177 Ile to Asp, near the monomer bacteriochlorophylls, were designed to result in the placement of a hydrogen bond donor group near the ring V keto carbonyl of each bacteriochlorophyll. Perturbations of the electronic structures of the bacteriochlorophylls in the mutants are indicated by additional resolved transitions in the bacteriochlorophyll absorption bands in steady-state low-temperature and time-resolved room temperature spectra in three of the resulting mutant reaction centers. The major effect of the two mutations near the dimer was an increase up to 80 mV in the donor oxidation-reduction midpoint potential. Correspondingly, the calculated free energy difference between the excited state of the primary donor and the initial charge separated state decreased by up to 55 mV, the initial forward electron-transfer rate was up to 4 times slower, and the rate of charge recombination between the primary quinone and the donor was ∼30% faster in these two mutants compared to the wild type. The two mutations near the monomer bacteriochlorophylls had minor changes of 25 mV or less in the donor oxidation-reduction potential, but the mutation close to the monomer bacteriochlorophyll on the active branch resulted in a roughly 3-fold decrease in the rate of the initial electron transfer.

Original languageEnglish
Pages (from-to)11029-11037
Number of pages9
JournalBiochemistry
Volume31
Issue number45
Publication statusPublished - 1992

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Bacteriochlorophylls
Rhodobacter sphaeroides
Mutation
Monomers
Viperidae
Dimers
Oxidation-Reduction
Electrons
Photosynthetic Reaction Center Complex Proteins
Temperature
Electron transitions
Excited states
Genetic Recombination
Free energy
Electronic structure
Absorption spectra
Hydrogen
Hydrogen bonds

ASJC Scopus subject areas

  • Biochemistry

Cite this

Williams, J. C., Alden, R. G., Murchison, H. A., Peloquin, J. M., Woodbury, N. W., & Allen, J. P. (1992). Effects of mutations near the bacteriochlorophylls in reaction centers from rhodobacter sphaeroides. Biochemistry, 31(45), 11029-11037.

Effects of mutations near the bacteriochlorophylls in reaction centers from rhodobacter sphaeroides. / Williams, J. C.; Alden, R. G.; Murchison, H. A.; Peloquin, J. M.; Woodbury, N. W.; Allen, James Paul.

In: Biochemistry, Vol. 31, No. 45, 1992, p. 11029-11037.

Research output: Contribution to journalArticle

Williams, JC, Alden, RG, Murchison, HA, Peloquin, JM, Woodbury, NW & Allen, JP 1992, 'Effects of mutations near the bacteriochlorophylls in reaction centers from rhodobacter sphaeroides', Biochemistry, vol. 31, no. 45, pp. 11029-11037.
Williams JC, Alden RG, Murchison HA, Peloquin JM, Woodbury NW, Allen JP. Effects of mutations near the bacteriochlorophylls in reaction centers from rhodobacter sphaeroides. Biochemistry. 1992;31(45):11029-11037.
Williams, J. C. ; Alden, R. G. ; Murchison, H. A. ; Peloquin, J. M. ; Woodbury, N. W. ; Allen, James Paul. / Effects of mutations near the bacteriochlorophylls in reaction centers from rhodobacter sphaeroides. In: Biochemistry. 1992 ; Vol. 31, No. 45. pp. 11029-11037.
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