ATPase motor

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... 

For review and evidence on ETS and OxPhos see M. Saraste Science 283 (5 March 1999) pp 1488-93 for ATPase motor see Paul D. Boyer (18 Nov 1999) "What matkes ATP synthase spin " Nature 402 247-8.)... 

Figure 1.6. The idling ATPase motor consumes the energy released on conversion of MgATP to MgADP and Pi without the performance of useful work. On binding MgATP to the globular apoprotein, a cleft, partially or entirely closed by association of oil-like groups, opens near the base of the...

The ATP molecule orients with its charged triphosphate tail at the base of the cleft such that it can access the water of the cleft. Because of this, water, which would normally form around the oil-like groups and effect reclosure, becomes oriented toward the phosphates and maintains the cleft in the open state. On hydrolysis of ATP and phosphate removal, the cleft partially or completely closes. Release of the ADP molecule recovers the original state to complete the cycle. Accordingly, energy has been consumed, but in this idling ATPase motor no work is accomplished. 

A First Step in Putting an ATPase Motor to Work,... 

Figure 2.16. An initial step in converting the idling ATPase motor into a motor capable of performing work involves attachment and detachment as between components of actin and myosin involved in the sliding filaments of muscle contraction. A The cartoon depicts an equilibrium between states of oil-like association and dissociation with fluctuating cleft openings, but in the absence of ATP, the equilibrium markedly shifts toward association.

Here, the standard free energy change per ATP molecule is equal to —50 pN nm at pH 7. The thermal energy at room temperature is equal to 4.1 pNnm. At intracellular conditions, [ATP] and [Pj] is in the order of 10 M. Therefore, for [ADP] of 50 /xM, AG is equal to —90.604 pN nm. Comparing this value of the free energy obtained by the hydrolysis of one molecule of ATP with the mechanical work done by the motor (i.e., 80 pN nm), we can deduce that the Fi -ATPase motor works on efficiency close to 100% ... 

Firestone AJ et al (2012) Small-molecule inhibitors of the AAA-r ATPase motor cytoplasmic dynein. Nature 484 125-129... 

Dynein, kinesin, and myosin are motor proteins with ATPase activity that convert the chemical bond energy released by ATP hydrolysis into mechanical work. Each motor molecule reacts cyclically with a polymerized cytoskeletal filament in this chemomechanical transduction process. The motor protein first binds to the filament and then undergoes a conformational change that produces an increment of movement, known as the power stroke. The motor protein then releases its hold on the filament before reattaching at a new site to begin another cycle. Events in the mechanical cycle are believed to depend on intermediate steps in the ATPase cycle. Cytoplasmic dynein and kinesin walk (albeit in opposite... 

Even though dynein, kinesin, and myosin serve similar ATPase-dependent chemomechanical functions and have structural similarities, they do not appear to be related to each other in molecular terms. Their similarity lies in the overall shape of the molecule, which is composed of a pair of globular heads that bind microtubules and a fan-shaped tail piece (not present in myosin) that is suspected to carry the attachment site for membranous vesicles and other cytoplasmic components transported by MT. The cytoplasmic and axonemal dyneins are similar in structure (Hirokawa et al., 1989 Holzbaur and Vallee, 1994). Current studies on mutant phenotypes are likely to lead to a better understanding of the cellular roles of molecular motor proteins and their mechanisms of action (Endow and Titus, 1992). 

Gibbons, l.R. (1988). Dynein ATPases as microtubule motors. J. Biol. Chem. 263, 15837-15840. 

Brady, S. T. A novel brain ATPase with properties expected for the fast axonal transport motor. Nature 317 73-75, 1985. 

KISc Kinesin motor, catalytic domain, ATPase E(MFP) 6(6) 20(20) 2NCD... 

The six ATPases belong to the rather large family of AAA ATPases (for ATPases Associated with a variety of cellular Activities) whose eukaryotic members include the motor protein dynein, the membrane fusion factor NSF, and the chaperone... 

Figure 9.21 The creatine/phosphocreatine shuttle in spermatozoa. This shuttle may not be present in all sperm it will depend upon the distance between the mitochondria and the flagellum. Mitochondria are present in the midpiece just below the head. ATP is required for movement of the flagellum which enables the sperm to swim. Dynein ATPase is the specific motor ATPase, similar to myosin ATPase, that transfers energy from ATP to the flagellum. A deficiency of creatine may explain low sperm motility in some infertile men. CK - creatine kinase. Deficiences of enzymes in the pathway for synthesis of creatine are known to occur (see Appendix 8.3).

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