Molecular motor

Source: Wikipedia, the free encyclopedia.
This article is about biological molecular motors. For man-made molecular motors, see Synthetic molecular motor.

biological machine that utilizes protein dynamics

Molecular motors are natural (biological) or artificial

thermal noise
are significant.

Examples

nanoscales to walk along a microtubule
.

Some examples of biologically important molecular motors:[2]

  • Cytoskeletal motors
    • Myosins are responsible for muscle contraction, intracellular cargo transport, and producing cellular tension.
    • anterograde transport
      .
    • retrograde transport
      .
  • 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:
Molecular dynamics simulation of a synthetic molecular motor composed of three molecules in a nanopore (outer diameter 6.7 nm) at 250 K.[4]

A recent study has also shown that certain enzymes, such as Hexokinase and Glucose Oxidase, are aggregating or fragmenting during catalysis. This changes their hydrodynamic size that can affect enhanced diffusion measurements.[14]

  • Synthetic molecular motors have been created by chemists that yield rotation, possibly generating torque.[15]

Organelle and vesicle transport

There are two major families of molecular motors that transport organelles throughout the cell. These families include the dynein family and the kinesin family. Both have very different structures from one another and different ways of achieving a similar goal of moving organelles around the cell. These distances, though only few micrometers, are all preplanned out using microtubules.[16]

  • Kinesin – These molecular motors always move towards the positive end of the cell
    • Uses ATP hydrolysis during the process converting ATP to ADP
      • This process consists of ...
        • The "foot" of the motor binds using ATP, the "foot" proceeds a step, and then ADP comes off. This repeats itself until the destination has been reached
    • The kinesin family consists of a multitude of different motor types
  • Dynein – These molecular motors always move towards the negative end of the cell
    • Uses ATP hydrolysis during the process converting ATP to ADP
    • Unlike kinesin, the dynein is structured in a different way which requires it to have different movement methods.
      • One of these methods includes the power stroke, which allows the motor protein to "crawl" along the microtubule to its location.
    • The structure of dynein consists of
      • A Stem Containing
        • A region that binds to dynactin
        • Intermediate/light chains that will attach to the dynactin bonding region
      • A Head
      • A Stalk
        • With a domain that will bind to the microtubule
These molecular motors tend to take the path of the microtubules. This is most likely due to the facts that the microtubules spring forth out of the centrosome and surround the entire volume of the cell. This in turn creates a "Rail system" of the whole cell and paths leading to its organelles.

Theoretical considerations

Part of a series on
Microbial and microbot movement
Microswimmers
Taxa
Taxis
Kinesis
Microbots and particles
Biohybrids
  • Biohybrid microswimmers
Collective motion
Molecular motors
Biological motors
Synthetic motors
Related

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:

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

Main article: Synthetic molecular motor

Recently,

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. One step toward understanding nanoscale dynamics was made with the study of catalyst diffusion in the Grubb's catalyst system.[18] Other systems like the nanocars
, while not technically motors, are also illustrative of recent efforts towards synthetic nanoscale motors.

Other non-reacting molecules can also behave as motors. This has been demonstrated by using dye molecules that move directionally in gradients of polymer solution through favorable hydrophobic interactions.[19] Another recent study has shown that dye molecules, hard and soft colloidal particles are able to move through gradient of polymer solution through excluded volume effects.[20]

See also

References

  1. S2CID 28061339
    .
  2. ^ Nelson P, Radosavljevic M, Bromberg S (2004). Biological physics. Freeman.
  3. PMID 11158567
    .
  4. PMID 25078022
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  5. PMID 12384568
    .
  6. S2CID 26171993
    .
  7. S2CID 28364947
    .
  8. S2CID 4424168
    .
  9. PMID 25486612
    .
  10. S2CID 52845451
    .
  11. S2CID 229411011
    .
  12. PMID 31263753
    .
  13. S2CID 249625518
    .
  14. S2CID 237507756
    .
  15. PMID 17133632
    .
  16. ISBN 978-1-4641-8339-3
    .
  17. PMID 38396042
    .
  18. PMID 26636667
    .
  19. PMID 29064685
    .
  20. S2CID 195879481
    .

External links
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