Abstract
~ ~ ~~ The H+-ATPase (ATP synthase, F,F,) of Escherichia coli, mitochondria or chloroplasts has a complicated structure with a defined stoi- chiometry (l-31: catalytic sector F1, a3fi3y&; and membrane sector F,, abzc10-12. The kinetic mechanism of the purified F1 sector or F1- ATPase has been clearly verified (4-61: uni-site (single site) and multi-site (steady state) catalysis can be measured in the presence of a sub-stoichiometric amount of ATP (ATP/Fl 10') respectively. On uni-site catalysis, ATP binds to a single cata- lytic site and is hydrolysed at a rate 105-106-fold lower than that of multi-site catalysis. The higher multi-site rate is due to the co-operativity between three catalytic sites in the The unique feature of this complicated enzyme is the energy coupling between catalysis and the electrochemical proton gradient. Protons transported through F, cause a series of con- formational changes of different FI subunits and drive ATP synthesis in the P subunit. In the reverse reaction, ATP hydrolysis causes the fl subunit conformational change, which is trans- mitted through other F1 subunits and finally transports protons through F,. In this article we discuss the catalysis and energy coupling of the E. coli enzyme with emphasis on the subunit- subunit interaction(s). subunits.
Published Version
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