Regulation of coupling factor in field-grown sunflower: A Redox model relating coupling factor activity to the activities of other thioredoxin-dependent chloroplast enzymes

David M. Kramer, Robert R. Wise, James R. Frederick, David M. Alm, John D. Hesketh, Donald R. Ort, Antony R. Crofts

Research output: Contribution to journalArticle

Abstract

Simultaneous, non-invasive measurements were made of the rate of photosynthetic CO2 fixation and the state of activation of the chloroplast CF1CF0-ATP synthase (CF) in field-grown sunflower (Helianthus annuus L.) during the dark-to-light transition at sunrise. CO2 fixation showed a linear response with light intensity from zero to about 500-700 μE m-2 s-1. However, at light intensities of only 5-22 μE m-2 s-1, the energetic threshold for activation of the CF was found to be significantly lowered (as compared to the pre-dawn state), presumably through reduction of the regulatory sulfhdryl groups of the γ-subunit of the CF. When these studies were extended to chamber-grown plants, it was found that as little as 5 seconds of illumination at 4 μE m-2 s-1 caused apparently full CF reduction. It is clear, therefore, that the catalytic activation of CF is not rate limiting to the induction of carbon assimilation under field conditions during a natural dark-to-light transition at sunrise. A model, based on the redox properties of the regulatory sulfhydryls, was developed to examine the significance of sulfhydryl midpoint potential in explaining the differences in light sensitivity and oxidation and reduction kinetics, between the CF and other thioredoxin-modulated chloroplast enzymes. Computer simulations of the light-induced regulation of three representative thioredoxin-modulated enzymes are presented.

Original languageEnglish (US)
Pages (from-to)213-222
Number of pages10
JournalPhotosynthesis research
Volume26
Issue number3
DOIs
StatePublished - Dec 1 1990

Fingerprint

Chloroplast Thioredoxins
Thioredoxins
Helianthus
Oxidation-Reduction
Helianthus annuus
chloroplasts
Light
Enzymes
enzymes
Chemical activation
light intensity
carbon dioxide
H-transporting ATP synthase
Chloroplast Proton-Translocating ATPases
Photophobia
computer simulation
Photosensitivity
lighting
Lighting
Computer Simulation

Keywords

  • ATP synthase
  • chloroplast coupling factor
  • induction
  • photosynthesis
  • regulation
  • thioredoxin

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology

Cite this

Regulation of coupling factor in field-grown sunflower : A Redox model relating coupling factor activity to the activities of other thioredoxin-dependent chloroplast enzymes. / Kramer, David M.; Wise, Robert R.; Frederick, James R.; Alm, David M.; Hesketh, John D.; Ort, Donald R.; Crofts, Antony R.

In: Photosynthesis research, Vol. 26, No. 3, 01.12.1990, p. 213-222.

Research output: Contribution to journalArticle

Kramer, David M. ; Wise, Robert R. ; Frederick, James R. ; Alm, David M. ; Hesketh, John D. ; Ort, Donald R. ; Crofts, Antony R. / Regulation of coupling factor in field-grown sunflower : A Redox model relating coupling factor activity to the activities of other thioredoxin-dependent chloroplast enzymes. In: Photosynthesis research. 1990 ; Vol. 26, No. 3. pp. 213-222.
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