Molecular motor

Molecular motor

Molecular motors are biological molecular machines that are the essential agents of movement in living organisms. Generally speaking, a motor may be defined as a device that consumes energy in one form and converts it into motion or mechanical work; for example, many protein-based molecular motors harness the chemical free energy released by the hydrolysis of ATP in order to perform mechanical work [1]. In terms of energetic efficiency, this type of motor can be superior to currently available man-made motors. One important difference between molecular motors and macroscopic motors is that molecular motors operate in the thermal bath, an environment where the fluctuations due to thermal noise are significant.

Contents

Examples

Some examples of biologically important molecular motors[2]:

  • Cytoskeletal motors
    • Myosin is responsible for muscle contraction
    • Kinesin moves cargo inside cells away from the nucleus along microtubules
    • Dynein produces the axonemal beating of cilia and flagella and also transports cargo along microtubules towards the cell nucleus
  • Polymerisation motors
    • Actin polymerization generates forces and can be used for propulsion. ATP is used.
    • Microtubule polymerization using GTP.
    • Dynamin is responsible for the separation of clathrin buds from the plasma membrane. GTP is used.
  • Rotary motors:
    • FoF1-ATP synthase family of proteins convert the chemical energy in ATP to the electrochemical potential energy of a proton gradient across a membrane or the other way around. The catalysis of the chemical reaction and the movement of protons are coupled to each other via the mechanical rotation of parts of the complex. This is involved in ATP synthesis in the mitochondria and chloroplasts as well as in pumping of protons across the vacuolar membrane[3]
    • The bacterial flagellum responsible for the swimming and tumbling of E. coli and other bacteria acts as a rigid propeller that is powered by a rotary motor. This motor is driven by the flow of protons across a membrane, possibly using a similar mechanism to that found in the Fo motor in ATP synthase.
  • Nucleic acid motors:
    • RNA polymerase transcribes RNA from a DNA template [4]
    • DNA polymerase turns single-stranded DNA into double-stranded DNA. [5][6]
    • Helicases separate double strands of nucleic acids prior to transcription or replication. ATP is used.
    • Topoisomerases reduce supercoiling of DNA in the cell. ATP is used.
    • RSC and SWI/SNF complexes remodel chromatin in eukaryotic cells. ATP is used.
    • SMC protein responsible for chromosome condensation in eukaryotic cells[7].
    • Viral DNA packaging motors inject viral genomic DNA into capsids as part of their replication cycle, packing it very tightly. [8]
  • Synthetic molecular motors have been created by chemists that yield rotation, possibly generating torque.

Theoretical Considerations

Because the motor events are stochastic, molecular motors are often modeled with the Fokker-Planck equation or with Monte Carlo methods. These theoretical models are especially useful when treating the molecular motor as a Brownian motor.

Experimental Observation

In experimental biophysics, the activity of molecular motors is observed with many different experimental approaches, among them:

  • Fluorescent methods: fluorescence resonance energy transfer (FRET), fluorescence correlation spectroscopy (FCS)
  • Magnetic tweezers can also be useful for analysis of motors that operate on long pieces of DNA
  • Neutron spin echo spectroscopy can be used to observe motion on nanosecond timescales
  • Optical tweezers are well-suited for studying molecular motors because of their low spring constants
  • Single-molecule electrophysiology can be used to measure the dynamics of individual ion channels

Many more techniques are also used. As new technologies and methods are developed, it is expected that knowledge of naturally occurring molecular motors will be helpful in constructing synthetic nanoscale motors.

Non-biological

Recently, chemists and those involved in nanotechnology have begun to explore the possibility of creating molecular motors de novo. These synthetic molecular motors currently suffer many limitations that confine their use to the research laboratory. However, many of these limitations may be overcome as our understanding of chemistry and physics at the nanoscale increases. Systems like the nanocars, while not technically motors, are illustrative of recent efforts towards synthetic nanoscale motors.

See also

References

  1. ^ Bustamante C, Chemla YR, Forde NR, Izhaky D (2004). "Mechanical processes in biochemistry". Annu. Rev. Biochem. 73: 705–48. doi:10.1146/annurev.biochem.72.121801.161542. PMID 15189157. 
  2. ^ Nelson, P.; M. Radosavljevic, S. Bromberg (2004). Biological physics. Freeman. 
  3. ^ Tsunoda SP, Aggeler R, Yoshida M, Capaldi RA (January 2001). "Rotation of the c subunit oligomer in fully functional F1Fo ATP synthase". Proc. Natl. Acad. Sci. U.S.A. 98 (3): 898–902. Bibcode 2001PNAS...98..898T. doi:10.1073/pnas.031564198. PMC 14681. PMID 11158567. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=14681. 
  4. ^ Dworkin J, Losick R (October 2002). "Does RNA polymerase help drive chromosome segregation in bacteria?". Proc. Natl. Acad. Sci. U.S.A. 99 (22): 14089–94. Bibcode 2002PNAS...9914089D. doi:10.1073/pnas.182539899. PMC 137841. PMID 12384568. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=137841. 
  5. ^ I. Hubscher, U.; Maga, G.; Spadari, S. (2002). "Eukaryotic DNA polymerases". Annual Review of Biochemistry 71: 133–63. doi:10.1146/annurev.biochem.71.090501.150041. PMID 12045093. 
  6. ^ Smith DE, Tans SJ, Smith SB, Grimes S, Anderson DL, Bustamante C (October 2001). "The bacteriophage straight phi29 portal motor can package DNA against a large internal force". Nature 413 (6857): 748–52. Bibcode 2001Natur.413..748S. doi:10.1038/35099581. PMID 11607035. 
  7. ^ Peterson C (1994). "The SMC family: novel motor proteins for chromosome condensation?". Cell 79 (3): 389–92. doi:10.1016/0092-8674(94)90247-X. PMID 7954805. 
  8. ^ Robert Sanders, Molecular motor powerful enough to pack DNA into viruses at greater than champagne pressures, researchers report, Press release, University of California

External links

  • Cymobase - A database for cytoskeletal and motor protein sequence information

Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • Motor protein — Motor proteins are a class of molecular motors that are able to move along the surface of a suitable substrate. They are powered by the hydrolysis of ATP and convert chemical energy into mechanical work. Contents 1 Cellular functions 2 Diseases… …   Wikipedia

  • Motor (disambiguation) — Motor is a device that creates motion. It usually refers to an engine of some kind. It may also specifically refer to: Electric motor, a machine that converts electricity into a mechanical motion AC motor, an electric motor that is driven by… …   Wikipedia

  • Molecular propeller — Pumping of water by the hydrophobic surface molecular propeller Molecular propeller is a molecule that can propel fluids when rotated, due to its special shape that is designed in analogy to macroscopic propellers [1] [2] …   Wikipedia

  • Motor — may refer to: *Engine **Motor car or automobile **Motor vehicle **Motorcycle, a term used by police officers to refer to their official duty motorcycles *Motor system, the physiological system that is responsible for physical movement **Motor… …   Wikipedia

  • Motor de combustión interna alternativo — Motor Otto 2T refrigerado por aire Motor de cuatro tiempos de gasolina, DOHC. Los motores de combustión interna alternativos, vulgarmente conocidos como motores de explosión …   Wikipedia Español

  • Motor oil — For the TV documentary focused on the Edmonton Oilers of the National Hockey League, see Oil Change (TV Series). Motor oil sample Motor oil or engine oil is an oil used for lubrication of various internal combustion engines. The main function is… …   Wikipedia

  • Molecular machine — Part of a series of articles on Molecular Nanotechnology …   Wikipedia

  • Motor molecular — Los motores moleculares son motores en los que los movimientos individuales de unas pocas moléculas son responsables de la conversión de una forma de energía ( principalmente química) en trabajo. En la naturaleza, están en el origen de todos los… …   Wikipedia Español

  • Synthetic molecular motors — are molecular machines capable of rotation under energy input. Although the term molecular motor has traditionally referred to a naturally occurring protein that induces motion, some groups also use the term when referring to non biological, non… …   Wikipedia

  • Electric motor — For other kinds of motors, see motor (disambiguation). For a railroad electric engine, see electric locomotive. Various electric motors. A 9 volt PP3 transistor battery is in the center foreground for size comparison. An electric motor converts… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”