Spectroscopic characterization of quinone-site mutants of the bacterial photosynthetic reaction center

Philip D. Laible, Yuenian Zhang, Andrea L. Morris, Seth W. Snyder, Clint Ainsworth, Scott R. Greenfield, Michael R Wasielewski, Pierre Parot, Barbara Schoepp, Marianne Schiffer, Deborah K. Hanson, Marion C. Thurnauer

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Site-specific mutations in the quinone binding sites of the photosynthetic reaction center (RC) protein complexes of Rhodobacter (R.) capsulatus caused pronounced effects on sequential electron transfer. Conserved residues that break the twofold symmetry in this region of the RC - M246Ala and M247Ala in the Q(A) binding pocket, and L212Glu and L213Asp in the Q(B) binding pocket - were targeted. We constructed a Q(B)-site mutant, L212Glu-L213Asp → Ala-Ala, and a Q(A)-site mutant, M246Ala-M247Ala → Glu-Asp, to partially balance the differences in charge distribution normally found between the two quinone binding sites. In addition, two photocompetent revertants were isolated from the photosynthetically-incompetent M246Glu-M247Asp mutant: M246Ala-M247Asp and M246Gly-M247Asp. Sequential electron transfer was investigated by continuous light excitation and time-resolved electron paramagnetic resonance (EPR), and time-resolved optical techniques. Several lines of EPR evidence suggested that the forward electron transfer rate to Q(A), k(Q), was slowed in those strains containing altered Q(A) sites. The slower rates of secondary electron transfer were confirmed by time-resolved optical results with the M246Glu-M247Asp mutations in the Q(A) site resulting in a dramatically lowered secondary electron transfer efficiency [k(Q) <(2 ns)-1] in comparison with either the native R. capsulatus RC or the Q(B) site mutant [k(Q) ≃ (200 ps)-1]. Secondary electron transfer in the two revertants was intermediate between that of the native RC and the Q(A) mutant. The P+Q(A)- → PQ(A) charge recombination rates were also changed in the strains that carried altered Q(A) sites. We show that local mutations in the Q(A) site, presumably through local electrostatic changes, significantly alter binding and electron transfer properties of Q(A).

Original languageEnglish
Pages (from-to)93-103
Number of pages11
JournalPhotosynthesis Research
Volume52
Issue number2
DOIs
Publication statusPublished - 1997

Fingerprint

photosynthetic reaction centers
Photosynthetic Reaction Center Complex Proteins
quinones
electron transfer
Electrons
mutants
electron paramagnetic resonance spectroscopy
Electron Spin Resonance Spectroscopy
mutation
Mutation
Paramagnetic resonance
binding sites
Rhodobacter
Binding Sites
Rhodobacter capsulatus
Charge distribution
benzoquinone
Static Electricity
Genetic Recombination
Electrostatics

Keywords

  • Electron paramagnetic resonance
  • Electron spin polarization
  • Electrostatics
  • Quinone binding
  • Revertant isolation

ASJC Scopus subject areas

  • Plant Science

Cite this

Laible, P. D., Zhang, Y., Morris, A. L., Snyder, S. W., Ainsworth, C., Greenfield, S. R., ... Thurnauer, M. C. (1997). Spectroscopic characterization of quinone-site mutants of the bacterial photosynthetic reaction center. Photosynthesis Research, 52(2), 93-103. https://doi.org/10.1023/A:1005806700335

Spectroscopic characterization of quinone-site mutants of the bacterial photosynthetic reaction center. / Laible, Philip D.; Zhang, Yuenian; Morris, Andrea L.; Snyder, Seth W.; Ainsworth, Clint; Greenfield, Scott R.; Wasielewski, Michael R; Parot, Pierre; Schoepp, Barbara; Schiffer, Marianne; Hanson, Deborah K.; Thurnauer, Marion C.

In: Photosynthesis Research, Vol. 52, No. 2, 1997, p. 93-103.

Research output: Contribution to journalArticle

Laible, PD, Zhang, Y, Morris, AL, Snyder, SW, Ainsworth, C, Greenfield, SR, Wasielewski, MR, Parot, P, Schoepp, B, Schiffer, M, Hanson, DK & Thurnauer, MC 1997, 'Spectroscopic characterization of quinone-site mutants of the bacterial photosynthetic reaction center', Photosynthesis Research, vol. 52, no. 2, pp. 93-103. https://doi.org/10.1023/A:1005806700335
Laible, Philip D. ; Zhang, Yuenian ; Morris, Andrea L. ; Snyder, Seth W. ; Ainsworth, Clint ; Greenfield, Scott R. ; Wasielewski, Michael R ; Parot, Pierre ; Schoepp, Barbara ; Schiffer, Marianne ; Hanson, Deborah K. ; Thurnauer, Marion C. / Spectroscopic characterization of quinone-site mutants of the bacterial photosynthetic reaction center. In: Photosynthesis Research. 1997 ; Vol. 52, No. 2. pp. 93-103.
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AU - Snyder, Seth W.

AU - Ainsworth, Clint

AU - Greenfield, Scott R.

AU - Wasielewski, Michael R

AU - Parot, Pierre

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