Mechanism for ATP synthase

Figure 5.19 Binding-change mechanism for ATP synthase. Rotation of the y subunit inter-converts the three-(3 subunits. The subunit in the tight (T) form contains newly synthesized ATP that cannot be released. Rotation by 120° converts it to the open (O) form, from which ATP can be released, allowing it to bind ADP and P, to begin a new cycle. (From Berg et al., 2001. Reproduced with permission from W.H. Freeman and Co.)...

Figure 18-15 Boyer s binding change mechanism for ATP synthase in a simple form. After Boyer245 but modified to include a central camshaft which may drive a cyclic alteration in conformations of the subunits. The small "pointer" on this shaft is not to be imagined as real but is only an indicator of rotation with induced conformational changes. The rotation could occur in 120° steps rather than the smaller steps suggested here.

Boyer, P. D. (1993). The binding change mechanism for ATP synthase Some probabilities and possibilities. Biochim. Biophys. Acta 1140, 215-250. 

Figure 18.32. Binding-Change Mechanism for ATP Synthase. The rotation of the y subunit interconverts the three P subunits. The subunit in the T (tight) form, which contains newly synthesized ATP that cannot be released, is converted into the O (open) form. In this form, it can release ATP and then bind ADP and Pj to begin a new cycle.

Figure 18-29 Binding-change mechanism for ATP synthase. The rotation of the 7 subunit interconveirls the three j3 subunits. The subunit in the T (tight) form interconverts ADP and P, and ATP but does not allow ATP be released. When the 7 subunit is rotated by 120 degrees in a cO Unterctockwise CCWJ direction, the T-form subunit is converted into the O formi, allowitng ATP release. ADP and Pj can tfien bind to the O-form subunit.

P.D. Boyer, The Binding Change Mechanism for ATP Synthase—Some Probabilities and Possibilities. Biochim. Biophys. Acta, 1140, 215-250, 1993. 

Boyer, P., A perspective of the binding change mechanism for ATP synthesis. FASEB J. 3 2164, 1989. A review of work on the ATP-synthase. 

Fig. 27. Illustration of the binding change mechanism for ATP synthesis by the proton-translocating ATP synthase. F, has three chemically identical but conformationally distinct Interacting subunits designated as 0" [open], "L" [loose] and "T [tight] see text forfurfher details on how the three catalytic [ap] sites pass through three conformational states driven by proton flux. Figure modeled after Cross (1981) The mechanism and reguiation of ATP synthesis by F -ATPases. Annu Rev Biochem 50 687.

Fig. 40. Two similar models for ATP synthase. (A) The Capaldi model shows cross-links between various Fq and F, subunits which result in blocking or not blocking enzymatic activity the open bow-ties are used to represent cross-links that do not affect the ATP synthase activity and the black bow-ties those that do. (B) The Junge model places emphasis on the structural sectors of the "motor" and the engine parts, the rotor and stator. See text for discussion. (A) Adapted from Ogilvie, Aggeler and Capaldi (1997) Cross-linking of the subunit to one of the three a subunits has no effect on functioning as expected if is a part of the stator that links the Fi and Fo ports of the Escherichia coliA TP synthase. J Biol Chem 272 16655 (B) Adapted from Junge, Lill and Engelbrecht (1997) A TP synthase an electrochemical transducer with rotatory mechanics. Trends in Biochem Sci 22 420. Also cf. model of Peter GrSber in color in Color Plate 17.

Fig. 21.4. Binding change mechanism for ATP synthesis. The three ap subunit pairs of the ATP synthase headpiece have binding sites that can exist in three different conformations, depending on the position of the 7 stalk subunit. Step 1 When ADP + Pi bind to an open site and the proton influx rotates the 7 spindle (represented by the arrow), the conformation of the subunits change and ATP is released from one site. (ATP dissociation is, thus, the energy-requiring step). Bound ADP and Pi combine to form ATP at another site. Step 2 As the ADP + Pi bind to the new open site, and the 7 shaft rotates, the conformations of the sites change again, and ATP is released. ADP and Pi combine to form another ATP.

Which of the following statements about the proposed mechanism for ATP synthesis by ATP synthase are correct ... 

The electrochemical potential difference is used to drive a membrane-located ATP synthase which in the presence of P + ADP forms ATP (Figure 12-8). Scattered over the surface of the inner membrane are the phos-phorylating complexes, ATP synthase, responsible for the production of ATP (Figure 12-1). These consist of several protein subunits, collectively known as F, which project into the matrix and which contain the phosphorylation mechanism (Figure 12-8). These sub-... 

Figure 12-9. Mechanism of ATP production by ATP synthase. The enzyme compiex consists of an Fq sub-compiex which is a diskof "C" protein subunits. Attached is a y-subunit in the form of a "bentaxie." Protons passing through the disk of "C" units cause it and the attached y-subunit to rotate. The y-subunit fits inside the F, subcompiex of three a- and three (3-sub-units, which are fixed to the membrane and do not rotate. ADP and P are taken up sequentiaiiy by the (3-subunits to form ATP, which is expeiied as the rotating y-subunit squeezes each (3-subunit in turn. Thus, three ATP moiecuies are generated per revoiution. For ciarity, not aii the subunits that have been identified are shown—eg, the "axie" aiso contains an e-subunit.

Fig. 4. Schematic diagram of the ApH - Aip two mutually non-colinear half-channel model for torque generation by the Fq portion of ATP synthase forming a part of the torsional mechanism of energy transduction and ATP synthesis [16-20,56]...

The molecular basis of site-site cooperativity in ATP synthase still remains unelucidated [46], and the absence of any direct evidence for cooperativity (despite almost three decades of effort) is explained, within the framework of the torsional mechanism, by the fact that site-site cooperativity does not exist in the physiological, steady state mode of functioning. Since, according to the torsional mechanism, no rotation takes place in uni-site or bi-site catalysis... 

FIGURE 11. Left simplified schematic diagram of a mitochondrial ATP-synthase. Adapted from Reference 97 with permission from AAAS. Right binding change mechanism for the synthesis of ATP... 

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