ISSN:
1573-6881
Keywords:
ATP synthase
;
F1F0 ATPase
;
energy transduction
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Physics
Notes:
Abstract The mitochondrial ATP synthases shares many structural and kinetic properties with bacterial and chloroplast ATP synthases. These enzymes transduce the energy contained in the membrane's electrochemical proton gradients into the energy required for synthesis of high-energy phosphate bonds. The unusual three-fold symmetry of the hydrophilic domain, F1, of all these synthases is striking. Each F1 has three identical β subunits and three identical α subunits as well as three additional subunits present as single copies. The catalytic site for synthesis is undoubtedly contained in the β subunit or an α, β interface, and thus each enzyme appears to contain three identical catalytic sites. This review summarizes recent isotopic and kinetic evidence in favour of the concept, originally proposed by Boyer and coworkers, that energy from the proton gradient is exerted not directly for the reaction at the catalytic site, but rather to release product from a single catalytic site. A modification of this binding change hypotheses is favored by recent data which suggest that the binding change is due to a positional change in all three β subunits relative to the remaining subunits of F1 and F0 and that the vector of rotation is influenced by energy. The positional change, or rotation, appears to be the slow step in the process of catalysis and it is accelerated in all F1F0 ATPases studied by substrate binding and by the proton gradient. However, in the mammalian mitochondrial enzyme, other types of allosteric rate regulation not yet fully elucidated seem important as well.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00762368
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