Boyer s binding change mechanism

Paul Boyer s binding change mechanism Transport Chain of Mitochondria... 

A simple version of Boyer s binding change mechanism is shown in Figure 18-15. The three F, p subunits are depicted in three different conformations. In O the active site is open, in T it is closed, and if ATP is present in the active site it is tightly bound. In the low affinity L conformation ligands are bound weakly. 

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.

Figure 10.18 Boyer s Binding Change Mechanism. The asymmetrical y subunit that causes changes in the structure of the /3 subunits can be seen in the center. [Courtesy of Dr. J.E. Walker.]...

In this chapter, we will describe the composition of the phosphorylating enzyme of chloroplasts as determined by SDS-gel electrophoresis and its structure as revealed by electron microscopy. These studies led to a preliminary model for the chloroplast ATP synthase. The remainder of the chapter will be devoted to two main topics (photo)phosphorylation powered by proton translocation as described by Mitchell s chemiosmotic theory V and recent investigations of the structure and function of the phos-phorylating enzyme in relation to Paul Boyer s binding-change mechanism and a model involving... 

FIGURE 19.4 (See color insert.) Boyer s binding change mechanism. 

Direct evidence for the last statement was obtained in a number of very important experiments carried out in Boyer s laboratory. Studying the Pf-H2 0 isotopic exchange reaction in uncoupled mitochondria, Boyer and his collaborators had demonstrated that, in the catalytic center of the mitochondrial ATPsynthase, there occurred numerous acts of the formation and rupture of the covalent bond between ADP and P . Boyer proposed that ATP formation in the catalytic center is simply the reversion of the ATP hydrolysis reaction, ATP + H2O ADP -h Pj. This conclusion follows from the experimental fact that ATPase catalyzes the incorporation of the isotope from H2O into Pf that appears in the medium. The main features of Boyer s binding-change mechanism of ATP synthesis were clearly formulated in [167] as follows ... 

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