Demonstration of a transitory tight binding of ATP and of committed Pi and ADP during ATP synthesis by chloroplasts
AUTOR(ES)
Smith, Daniel J.
RESUMO
Rapid mixing, quenching, and filtration experiments with chloroplast thylakoid membranes, with energization by acid-base transition, demonstrate that an ATP tightly bound to the isolated membranes is a transient intermediate in the catalytic sequence for ATP synthesis. The experiments also show that most of the Pi and ADP bound at a catalytic site is committed to ATP formation without interchange with medium Pi or ADP. Other results give evidence that upon energization, the tightly bound ADP that is detectable in isolated thylakoid membranes or coupling factor ATPase is rapidly released to the medium from a catalytic site. These findings support an alternating site model in which an energy-requiring conformational transition loosens ATP binding at one site and simultaneously promotes Pi and ADP binding at the other site in a manner favoring ATP formation.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=431442Documentos Relacionados
- F1-ATPase-catalyzed synthesis of ATP from oleoylphosphate and ADP.
- Cooperative binding of ATP and MgADP in the sulfonylurea receptor is modulated by glibenclamide
- Demonstration of Photophosphorylation by Maize Chloroplasts 12
- Characterization of external electric field-driven ATP synthesis in chloroplasts
- Influence of Photorespiration on ATP/ADP Ratios in the Chloroplasts, Mitochondria, and Cytosol, Studied by Rapid Fractionation of Barley (Hordeum vulgare) Protoplasts 1
