Biology rotary motor

Campbell, P.N., Smith, A.D. and Peters, T.J. (2005) Biochemistry Illustrated Biochemistry and Molecular Biology in the Post-Genomic Era, 5th edition, Elsevier, London and Oxford, 242 pp. Capaldi, R. and Aggeler, R. (2002) Mechanism of FjF0-type ATP synthase, a biological rotary motor, TIBS, 27, 154-160. 

Fig. 2 A schematic representation of ATP synthase, a biological rotary motor, y (and c) are mobile whereas the aggregate a3 33 is fixed to the membrane and constitutes the stator of the motor.

Capaldi, R.A., and Aggeler, R. 2002. Mechanism of the FIFO-type ATP synthase, a biological rotary motor. Trends Biochem. Sci. 27 154—160. 

Linear and rotary motors of several types are very common in biology.62 Some examples of linear motors are the myosin-actin complex present in muscles63 or the kinesin-containing systems,64 while examples of rotary motors are provided by the enzyme ATP synthase65 or the motor responsible of mobility of bacterial flagella.66... 

Fig. la-e. Biological examples of molecular motors. Motors shown in a and b are rotary motors and c-e are linear motors. Motion takes place in the direction indicated by the arrows, and diagrams are not drawn to scale (reproduced with permission from [15])... 

In the last few years, however, the outstanding development of single molecule manipulation and observation, particularly by fluorescence spectroscopy, has thrown some light on the operational mechanism of several biological machines. For example, it was shown that ATP synthase, the enzyme that manufactures adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and inorganic phosphate (Pi) is powered by a rotary motor fueled by a proton gradient (Fig. 1). The asymmetric membrane-spanning Fq portion of the enzyme contains a proton channel, and the soluble F] portion contains three catalytic sites that cooperate in the... 

As represented schematically in Figure 8.26, ATP synthase contains a basic set of components that are common throughout biology. There are two rotary motors, the membranous Fo-motor and the extramembranous Fi-motor. An extramembranous rotor driven by the membranous Fo-motor couples rotations in each motor and drives ATP synthesis in the extramembranous Fi-motor. The effective housings of the two rotary motors are held fixed, one with respect to the other, by a stator element. In this way one complete rotation in the Fo-motor accomplishes one complete rotation in the Fi-motor. 

A molecular machine, a machine at the molecular level, is defined as a discrete number of molecular components that perform mechanical-like movements (output) in response to specific stimuli (input). Molecular machines include both naturally occurring devices found in biological systems and artificial molecular machines. There are many molecular machines in biological systems. Among the most prominent examples of molecular machines in living organisms are the muscle linear and ATPase rotary motors. In order to develop artificial machinery, scientists have constructed a variety of molecular and supramolecular systems with differences in shape, switching processes, or movements... 

Although this molecular motor does not achieve continuous and fast rotation, the design principles may prove relevant for a better understanding of biological molecular motors producing unidirectional rotary motion. 

Of particular interest with respect to applications in nanotechnology is the rotary supramolecular motor, FoFi-ATP synthase (Figure 1) (S). This enzyme is actually a double rotary motor. Proton flux across the membrane drives rotation of the Fo unit and the y spindle of the Fi unit. Rotation of the y spindle within the stationary Fi unit, in turn, drives the synthesis of ATP from ADP and inorganic phosphate. While the rotary motion of this device qualifies it as a motor, this motion is merely a mechanism, enabling its biological function as a factory for a ubiquitous fuel needed by cells. 

Molecular systems that exhibit controlled or coordinated rotary motion are discussed in this chapter. These systems represent a reproduction of a variety of macroscopic mechanical devices on the molecular scale. From gears to a motor, passing through a turnstile, a brake and a ratchet, we describe their design, synthesis and dynamic behavior. The importance of molecular motors in the biological realm and possible applications in nanotechnology are also discussed. 

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