PMID: 37901Jul 10, 1979

Light dependence of the decay of the proton gradient in broken chloroplasts

Biochimica Et Biophysica Acta
Y HoJ H Wang

Abstract

The initial rates and steady-state values of proton uptake by broken chloroplasts have been measured as functions of light intensity at various concentrations of chlorophyll, pyocyanine, supporting electrolyte, buffer, as well as pH and temperature. Kinetics analysis of the data shows that the rate of decay of proton gradient due to backward leakage depends on light intensity. Under steady illumination, the decay constant kL is equal to kD + mR0, where R0 is the initial rate of proton uptake which is a function of light intensity, kD is the decay constant in the dark and m is a parameter which is independent of light intensity. Treatment of chloroplasts with lysolecithin, neutral detergent, 2,4-dinitrophenol, or valinomycin in the presence of K+ increases kD without affecting m. Treatment with N,N'-dicyclohexylcarbodiimide or adenylyl imidodiphosphate under appropriate conditions decreases m without affectsity and hence m = 0. These results suggest that the light-dependent part (mR0) of kL is due to leakage of protons through the coupling factor (CF1-CF0) complex which can open or close depending on light intensity and that the light independent part (kD) of the decay constant kL is due to proton leakage elsewhere.

References

Jun 1, 1977·Proceedings of the National Academy of Sciences of the United States of America·N NelsonC Gitler
Feb 17, 1975·Biochimica Et Biophysica Acta·C CarmeliA Gepshtein
May 28, 1968·Biochimica Et Biophysica Acta·S J Karlish, M Avron
Nov 1, 1970·The Journal of Cell Biology·S Murakami, L Packer

Related Concepts

Mg-5'-Adenylylimidodiphosphate
Chlorophyll
Etioplasts
Darkness
Dicyclohexylcarbodiimide
Respiratory Chain
Hydrogen-Ion Concentration
Light
Lysophosphatidylcholines
Magnesium

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