F -ATPase

Dupuis, A., Israel, J.-P., Vignais, P.V. (1989). Direct identification of the fluoroaluminate and fluoroberyllate species responsible for inhibition of the mitochondrial F,- ATPase. FEBS Lett. 255,47-52. 

F-ATPases (including the H+- or Na+-translocating subfamilies F-type, V-type and A-type ATPase) are found in eukaryotic mitochondria and chloroplasts, in bacteria and in Archaea. As multi-subunit complexes with three to 13 dissimilar subunits, they are embedded in the membrane and involved in primary energy conversion. Although extensively studied at the molecular level, the F-ATPases will not be discussed here in detail, since their main function is not the uptake of nutrients but the synthesis of ATP ( ATP synthase ) [127-130]. For example, synthesis of ATP is mediated by bacterial F-type ATPases when protons flow through the complex down the proton electrochemical gradient. Operating in the opposite direction, the ATPases pump 3 4 H+ and/or 3Na+ out of the cell per ATP hydrolysed. 

Dimroth, P., Wang, H., Grabe, M. and Oster, G. (1999). Energy transduction in the sodium F-ATPase of Propionigenium modestum, Proc. Natl Acad. Sci. USA, 96, 4924-4929. 

Mixtures of proteins, natural and polymerizable lipids can be transferred into liposomes and polymerized hereafter. Initial experiments have shown that even very complex proteins such as F F.-ATPase can be incorporated in polymeric liposomes by this method under retention of the activity of the protein (76). 

F -ATPase Driven Nanomotors. Another type of biological driven engine is that of Fi-adenosine triphosphate synthease (Fi-ATPase) which hydrolyzes the ATP in the surrounding medium. Kinosita Jr. et al. observed the rotation of an actin filament attached to the Fi - ATPase motor. Later, Montemagno followed with the incorporation of a nickel nanorod with the Fi-ATPase motor. The outcome was the rotation of the... 

F,F ATPase COMPLEX REACTION ELEMENTARY REACTION PRIMITIVE CHANGE PARALLEL REACTIONS SERIES REACTIONS OOMPONENT... 

Cellular ATP synthetic activities of F -ATPase deletion mutants... 

FIGURE 11-39 Structure of the F F] ATPase/ATP synthase. F-type ATPases have a peripheral domain, F, consisting of three cr subunits, three j3 subunits, one S subunit (purple), and a central shaft (the y subunit, green). The integral portion of F-type ATPases, F0 (yellow), has multiple copies of c, one a, and two b subunits. F0 provides a transmembrane channel through which about four protons are pumped (red arrows) for each ATP hydrolyzed on the j3 subunits of F,. The remarkable mechanism by which these two events are coupled is described in detail in Chapter 19. It involves rotation of F0 relative to F, (black arrow). The structures of V0Vi and AoA, are essentially similar to that of F0F, and the mechanisms are probably similar, too. 

The idea of conformational coupling of ATP synthesis and electron transport is especially attractive when we recall that ATP is used in muscle to carry out mechanical work. Here we have the hydrolysis of ATP coupled to motion in the protein components of the muscle. It seems reasonable that ATP should be formed as a result of motion induced in the protein components of the ATPase. Support for this analogy has come from close structural similarities of the F, ATPase P subunits and of the active site of ATP cleavage in the muscle protein myosin (Chapter 19). 

Figure 10.19 ATP-fueled rotation of fluorescently labeled actin that is attached to the y subunit of the F,-ATPase by a streptavidin-biotin linker. The /3 subunits are immobilized on a microscope slide. [Modified from H. Noji, R. Yasuda, M. Yoshida, and K. Kinosita, Nature 386,299 (1997).]...

Racker isolated F, ATPase from mitochondria and reconstituted oxidative phosphorylation in submitochondrial vesicles. 

All five subunits of the E. coli F, ATPase have been purified, and the primary sequence of the a-subunit has been determined. ATPase activity could be reconstituted from the a-, p- and y-subunits. Subunits j3 and y from R. rubrum have been purified and reincorporated into the depleted membrane with full activity.302 The a- and /3-subunits contain sites for nucleotides.303 The sensitivity of the a-subunit of E. coli to trypsin hydrolysis differs when the high affinity site for ATP is saturated, suggesting that binding of ATP produces conformational changes.304... 

The F-, V-, and A-ATPases constitute a family of ATP hydrolysis-driven ion pumps which are found in Archaea, eubacteria, simple eukaryotes such as yeast, and higher eukaryotes including plants and mammals. The family of ion pumps is divided into three subfamilies the F-ATPases (which function mainly as ATP synthases), the vacuolar ATPases (which function solely as ATP hydrolysis-driven ion pumps) and the Archaeal A-type ATPases (whose function can be either in the direction of ATP synthesis or hydrolysis). All three members of the family are evolutionarily related, and it is believed that the three subfamilies have arisen from a common ancestor. 

A unique feature of the F/V/A-ATPases is that they are rotary molecular motor enzymes. This has been shown by experiment for members of the F-and V-ATPase subfamilies and is generally assumed to be true for the closely related A-ATPases as well. The two enzymatic processes, ATP synthesis/hydrolysis and ion translocation, are coupled via a rotational motion of a central domain of the complex (the rotor) relative to a static domain (the stator). The A-, F-, and V-ATPases represent the smallest rotary motors found in the living cell so far. Most of what we know about the structure and mechanism of these microscopic energy converters comes from studies conducted with the F-ATPase. In the following review, current structural knowledge for all three members of the family of F-, V-,... 

V-ATPase A-ATPasea Thermoplasma acidophilum F-ATPase Escherichia coli... 

The subunit nomenclature for the A-ATPase is Kfor the proteolipid, I for the V- and F-ATPase a-subunit, and C for the V-ATPase subunit d. The small polypeptide called H in the A-ATPase is probably the homologue of the V-ATPase G-subunit. 

AThe subunit has been confirmed for the insect (Merzendorfer et al, 1999) and chromaffin granule enzyme (Ludwig et al, 1998) and has recently been found in the yeast enzyme (Sambade and Kane, 2004). The subunit compositions of the F-ATPase from the bacterium Escherichia coli, the vacuolar ATPase from yeast and bovine brain clathrin-coated vesicles, and the A-ATPase from the Archaeon Thermoplasma acidophilum are listed. Molecular masses are calculated from the amino acid sequence where available. 

F- and V-ATPase are evolutionarily related (Gogarten et al., 1989 Nelson and Taiz, 1989). This relationship between F- and V-ATPases was first described based on the similarity of the amino acid sequence of the V-ATPase A- and B-subunits and the F-ATPase jS- and a-subunits,... 

II. Overall Structural Features of the F-, V-, and A-ATPases A. Structure of the F-ATPase... 

The nucleotide occupancy of the catalytic sites observed in the first crystal structure was exactly what Paul Boyer had predicted earlier in his binding-change model of cooperative catalysis (Boyer, 1993). Consequently, this first high-resolution structure of the Fj-ATPase immediately initiated a number of studies that ultimately led to the elucidation of the F -. TPase s rotational mechanism of cooperative catalysis. At the time, the F - ATPase structure represented the largest asymmetric structure solved to atomic resolution by x-ray crystallography, and this accomplishment, together with the visionary prediction of rotary catalysis, was subsequently awarded the 1997 Nobel prize in chemistry (to John Walker for the structure and Paul Boyer for the catalytic mechanism). However, whether the first (and many subsequent) structure (s) represented physiologically... 

At the time of this writing, there is no high-resolution structural model available for the intact membrane domain of the F-ATPase. The atomic resolution structure of the monomeric ( -subunit dissolved in organic solvent has been determined by nuclear magnetic resonance (NMR) spectroscopy at neutral and acidic pH (Girvin et al., 1998 Rastogi and Girvin,... 

What is known is that the ( -subunits from different species are able to form rings of between 10 and 14 proteolipids. For example, the x-ray crystal structure of the yeast F-ATPase (Stock et at, 1999) shows that there are 10 e-subunits, whereas the chloroplast enzyme has 14 (Seelert et at,... 

Figure 3A shows electron microscopy of the intact E. coli F-ATPase. Combining the low-resolution electron density maps derived by electron microscopy with the high-resolution structural information available for various subunits and their domains allows us to construct a high-resolution structural model of the intact E. coli FjF0-ATP synthase as shown in Fig. 3B. 

Fig. 3. Electron microscopy of the Escherichia coli FjFo-ATP synthase and the bovine brain vacuolar ATPase (A) Projection image of the E. coli F-ATPase (Wilkens, 2000). The positions of subunit a (large black arrowhead), the peripheral stalk (white arrow), the C-terminal domain of the 6-subunits (white arrowhead), and the 5-subunit (small black...

The Vo is made of subunits acc c"de. Subunits c, c, and c" are proteolipid isoforms each containing one essential lipid-exposed glutamate residue. The proteolipids in the V-ATPase are twice the size compared with the F-ATPase proteolipids, and it is assumed that the four transmembrane a helix c- and c -subunits are a result of an early gene fusion event. Subunit c" has two lipid-exposed glutamates, but only one of them is essential for proton pumping. The 100-kDa subunit a is a two-domain protein with a... 

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