What are Motor Proteins?

Motor Proteins in Mechanobiology

4.1 Introduction – What are Motor Proteins?

Motor proteins bind to and move along the cytoskeletal filaments and also bind to and hydrolyze nucleotides (reviewed in [1]). Nucleotide hydrolysis and controlled inorganic phosphate release by motor proteins causes restructuring of core domains that control the association of the motor protein with the filaments, other proteins, and the fresh supply of nucleotides.

Motor proteins propel themselves along the cytoskeleton using a mechanochemical cycle of filament binding, conformational change, filament release, conformation reversal, and filament rebinding. In most cases, the conformational change(s) on the motor protein prevents subsequent nucleotide binding and/or hydrolysis until the prior round of hydrolysis and release is complete.

Controlled hydrolysis of nucleotides and inorganic phosphate release by motor proteins can generate mechanical forces that can be used for:
  • translocating the motor proteins themselves along the filaments
  • stabilizing and/or moving the filaments (i.e., contractile stress fibers)
  • escorting cargo that is attached to the motor protein (e.g., vesicles, organelles, other proteins) to specific regions in the cell
In most cases, motor proteins transport substances in a particular direction, or polarity, along the filaments. This directionality is achieved by specific conformational changes that allow movement in only one direction.

Common motor proteins include; myosin, kinesin and dynein.

References

  1. Hwang W. & Lang MJ. Mechanical design of translocating motor proteins. Cell Biochem. Biophys. 2009; 54(1-3):11-22. [PMID: 19452133]
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Steven Wolf,
Mar 23, 2012, 12:30 AM