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Proton translocation induced by ATPase activity in chloroplasts
1Department of Biochemistry, Tel-Aviv University, Tel-Aviv, Israel
FEBS Letters
|April 16, 1970
Summary
Light activates proton uptake in chloroplasts via ATPase activity. This process, consistent with chemiosmotic theory, shows a proton to inorganic phosphate ratio that can be altered by gramicidin.
Area of Science:
- Biochemistry
- Plant Physiology
- Bioenergetics
Background:
- Chloroplasts utilize light energy for ATP synthesis.
- Chemiosmotic theory explains ATP production via proton gradients.
Purpose of the Study:
- To investigate proton (H+) uptake mechanisms in chloroplasts.
- To determine the stoichiometry of proton uptake relative to ATP hydrolysis.
- To assess the impact of ionophores on these processes.
Main Methods:
- Measuring light-triggered ATPase activity in chloroplasts.
- Quantifying proton uptake rates.
- Determining inorganic phosphate (P(i)) release from ATP.
- Utilizing gramicidin to modulate membrane permeability.
Main Results:
- Light-induced ATPase activity drives proton uptake.
- An initial H+/P(i) ratio of approximately two was observed.
- Gramicidin increased ATPase activity and lowered the H+/P(i) ratio to 1.4.
Conclusions:
- The observed proton uptake and H+/P(i) stoichiometry support the chemiosmotic model of energy coupling in chloroplasts.
- Membrane transport, influenced by factors like gramicidin, plays a crucial role in regulating proton gradients and ATP synthesis.