Complete tracking of transient proton flow through active chloroplast ATP synthase

Journal Article · Thu Oct 01 04:00:00 EDT 1987 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.84.20.7084· OSTI ID:7177624

Junge, W

Proton pumping in thylakoid membranes and backflow of protons through the active ATP synthase CF0-CF1 were investigated by flash spectrophotometry. A steady pH difference across the membrane was generated by continuous measuring light, supplemented by voltage transients that were generated by flashing light. In the presence of P/sub i/ and ADP, the electric potential transients elicited transients of proton flow via CF0-CF1. Proton flow was blocked by CF0-CF1 inhibitors: N,N'-dicyclohexylcarbodiimide, acting on the channel component CF0, and tentoxin, acting on the catalytic component CF1. The half-rise time was 40 ms in /sup 1/H/sub 2/O and 78 ms in /sup 2/H/sub 2/O. ATP synthesis under conditions of flashing light and transient proton flow was characterized by a K/sub m/(P/sub i/) of only 14 ..mu..M, contrasting with a K/sub m/ of several hundred micromolar for continuous ATP synthesis at high rate. This might reflect a resistance to P/sub i/ diffusion. The degree of proton delocalization in the chemiosmotic coupling between redox reactions and ATP synthesis is under debate. In this work, transient proton flow by way of CF0-CF1 was completely tracked from the lumen, across the membrane, and into the suspending medium. Proton uptake from the lumen and charge flow across the membrane occurred synchronously and in stoichiometric proportion. Pumps and ATP synthase were coupled through the lumen without involvement of intramembrane domains.

• Research Organization: Universitaet Osnabrueck (Germany, F.R.)
• OSTI ID: 7177624
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 84:20; ISSN PNASA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
ATP
BARYONS
BIOCHEMICAL REACTION KINETICS
BIOSYNTHESIS
CELL CONSTITUENTS
CHEMICAL REACTIONS
CHLOROPLASTS
ELEMENTARY PARTICLES
ENZYMES
FERMIONS
FOOD
HADRONS
HEAVY WATER
HYDROGEN COMPOUNDS
KINETICS
LIGASES
MEMBRANE TRANSPORT
NUCLEONS
NUCLEOTIDES
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PEAS
PH VALUE
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PLANTS
PROTONS
REACTION KINETICS
SYNTHESIS
VEGETABLES
WATER