Energy‐dependent transformation of the catalytic activities of the mitochondrial F<sub>0</sub>·F<sub>1</sub>‐ATP synthase

Galkin, Mikhail A.; Vinogradov, Andrei D.

doi:10.1016/s0014-5793(99)00347-6

Cited by 38 publications

(23 citation statements)

References 29 publications

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“…It is only certain that the activation probability was the highest in the presence of both ADP and P i . A similar finding was reported by Vinogradov and colleagues (29,30), that is, a submitochondrial particle containing the FoF 1 -ATPase showed a higher ATP-hydrolysis activity after transient charging of the membrane potential. The most plausible explanation is that when F 1 is rotated in the ATP-synthetic direction in the presence of the ADP and P i , the F 1 follows the ATP synthesis pathway to be efficiently activated.…”

Section: Angle Deviation Between the ␥-Subunit And The Magnetic Beadssupporting

confidence: 87%

Activation of pausing F ₁ motor by external force

Hirono-Hara

Ishizuka

Kinosita

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

102

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A rotary motor F1, a catalytic part of ATP synthase, makes a 120°s tep rotation driven by hydrolysis of one ATP, which consists of 80°a nd 40°substeps initiated by ATP binding and probably by ADP and͞or Pi dissociation, respectively. During active rotations, F1 spontaneously fails in ADP release and pauses after a 80°substep, which is called the ADP-inhibited form. In the present work, we found that, when pushed >؉40°with magnetic tweezers, the pausing F1 resumes its active rotation after releasing inhibitory ADP. The rate constant of the mechanical activation exponentially increased with the pushed angle, implying that F1 weakens the affinity of its catalytic site for ADP as the angle goes forward. This finding explains not only its unidirectional nature of rotation, but also its physiological function in ATP synthesis; it would readily bind ADP from solution when rotated backward by an Fo motor in the ATP synthase. Furthermore, the mechanical work for the forced rotation was efficiently converted into work for expelling ADP from the catalytic site, supporting the tight coupling between the rotation and catalytic event.ADP inhibition ͉ ATP synthase ͉ F1-ATPase ͉ magnetic tweezers ͉ single-molecule observation

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Section: Angle Deviation Between the ␥-Subunit And The Magnetic Beadssupporting

confidence: 87%

Activation of pausing F ₁ motor by external force

Hirono-Hara

Ishizuka

Kinosita

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

102

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“…We concluded that CF 0 F 1 did not catalyze uncoupled ATP hydrolysis and that, therefore, no corrections for uncoupled ATP hydrolysis were required. For MF 0 F 1 as well, the presence of a strong preactivation by Δμ H þ has been reported (24). However, with MF 0 F 1 small rates of ATP hydrolysis were detected in the presence of nigericin at Q values ≥1.87, and these rates increased with increasing Q value.…”

Section: Resultsmentioning

confidence: 79%

Comparison of the H ⁺ /ATP ratios of the H ⁺ -ATP synthases from yeast and from chloroplast

Petersen

Förster

Turina

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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F 0 F 1 -ATP synthases use the free energy derived from a transmembrane proton transport to synthesize ATP from ADP and inorganic phosphate. The number of protons translocated per ATP (H + /ATP ratio) is an important parameter for the mechanism of the enzyme and for energy transduction in cells. Current models of rotational catalysis predict that the H + /ATP ratio is identical to the stoichiometric ratio of c-subunits to β-subunits. We measured in parallel the H + /ATP ratios at equilibrium of purified F 0 F 1 s from yeast mitochondria (c/β = 3.3) and from spinach chloroplasts (c/β = 4.7). The isolated enzymes were reconstituted into liposomes and, after energization of the proteoliposomes with acid-base transitions, the initial rates of ATP synthesis and hydrolysis were measured as a function of ΔpH. The equilibrium ΔpH was obtained by interpolation, and from its dependency on the stoichiometric ratio,, finally the thermodynamic H + /ATP ratios were obtained: 2.9 ± 0.2 for the mitochondrial enzyme and 3.9 ± 0.3 for the chloroplast enzyme. The data show that the thermodynamic H + /ATP ratio depends on the stoichiometry of the c-subunit, although it is not identical to the c/β ratio. chemiosmotic theory | protonmotive force | bioenergetics | nanomachine C ells of all life kingdoms use H + -ATP synthases to produce the cellular energy carrier ATP from the energy of a transmembrane electrochemical potential difference of protons built up and maintained by proton transport mechanisms, such as the oxidative electron transport in mitochondria or the photoinduced electron transport in chloroplasts (1). The number of protons translocated for each synthesized ATP molecule (H + / ATP ratio) determines how large this difference of proton potential needs to be to maintain the high ATP/ADP ratio required by cell life. It is a key parameter in determining the flow of energy conversions in all living organisms. Ever since compelling experimental evidence in favor of a rotational mechanism for ATP synthases appeared (2-10), picturing them as molecular nanomachines in which two differently stepped motors (the membrane-embedded c-oligomer and the tripartite catalytic head) are connected by a central rotating shaft (γ/ε subunits), the general assumption has been that the H + /ATP ratio should coincide with the ratio of the number of proton-binding c-subunits to the three catalytic nucleotide-binding β-subunits. Structural data have shown that the number of c-subunit monomers varies according to species (ref. 11 and references therein), with numbers that are mostly not multiples of three. Consequences of the above assumption are (i) the H + /ATP ratio can vary among different species, and (ii) the H + /ATP ratio can be a noninteger number. The number of β-subunits is three in all F 0 F 1 analyzed so far, and the number of c-subunits varies between 8 and 15, resulting in predicted H + /ATP ratios between 2.7 and 5.0. To our knowledge, neither of the two assumptions above has yet been experimentally challenged with the required accu...

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“…Presumably, the inhibited structure represents one of the most stable forms of this enzyme, and is separated by a relatively small activation barrier from the major kinetic pathway of the hydrolysis reaction. In this regard, it is worth noting that MgADP inhibition does not operate during synthesis (Boyer 1997(Boyer , 2000, and synthesis renders inhibited enzyme back to a form capable of hydrolysis (Galkin & Vinogradov 1999). Free energy obtained by clockwise rotation of g will lift the enzyme from the bottom of the potential well back to the major pathway, or to a possibly di¡erent path for the synthesis.…”

Section: (A) Three Modes Of Hydrolysis Reactionmentioning

confidence: 99%

A rotary molecular motor that can work at near 100% efficiency

Kinosita

Yasuda

Noji

et al. 2000

Phil. Trans. R. Soc. Lond. B

226

141

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A single molecule of F 1 -ATPase is by itself a rotary motor in which a central g-subunit rotates against a surrounding cylinder made of a 3 b 3 -subunits. Driven by the three bs that sequentially hydrolyse ATP, the motor rotates in discrete 1208 steps, as demonstrated in video images of the movement of an actin ¢lament bound, as a marker, to the central g-subunit. Over a broad range of load (hydrodynamic friction against the rotating actin ¢lament) and speed, the F 1 motor produces a constant torque of ca. 40 pN nm. The work done in a 1208 step, or the work per ATP molecule, is thus ca. 80 pN nm. In cells, the free energy of ATP hydrolysis is ca. 90 pN nm per ATP molecule, suggesting that the F 1 motor can work at near 100% e¤ciency. We con¢rmed in vitro that F 1 indeed does ca. 80 pN nm of work under the condition where the free energy per ATP is 90 pN nm. The high e¤ciency may be related to the fully reversible nature of the F 1 motor: the ATP synthase, of which F 1 is a part, is considered to synthesize ATP from ADP and phosphate by reverse rotation of the F 1 motor. Possible mechanisms of F 1 rotation are discussed.

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Energy‐dependent transformation of the catalytic activities of the mitochondrial F₀·F₁‐ATP synthase

Cited by 38 publications

References 29 publications

Activation of pausing F ₁ motor by external force

Activation of pausing F ₁ motor by external force

Comparison of the H ⁺ /ATP ratios of the H ⁺ -ATP synthases from yeast and from chloroplast

A rotary molecular motor that can work at near 100% efficiency

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Energy‐dependent transformation of the catalytic activities of the mitochondrial F0·F1‐ATP synthase

Cited by 38 publications

References 29 publications

Activation of pausing F 1 motor by external force

Activation of pausing F 1 motor by external force

Comparison of the H + /ATP ratios of the H + -ATP synthases from yeast and from chloroplast

A rotary molecular motor that can work at near 100% efficiency

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Energy‐dependent transformation of the catalytic activities of the mitochondrial F₀·F₁‐ATP synthase

Activation of pausing F ₁ motor by external force

Activation of pausing F ₁ motor by external force

Comparison of the H ⁺ /ATP ratios of the H ⁺ -ATP synthases from yeast and from chloroplast