Editing Microtubule (section)

===Motor proteins===
[[File:CytoplasmicDyneinOnMT noLabels.png|thumb|A cytoplasmic dynein motor bound to a microtubule.]]
[[File:Kinesin cartoon.png|thumb|A kinesin molecule bound to a microtubule.]]
Microtubules can act as substrates for motor proteins that are involved in important cellular functions such as vesicle trafficking and cell division. Unlike other microtubule-associated proteins, motor proteins utilize the energy from ATP hydrolysis to generate mechanical work that moves the protein along the substrate. The major motor proteins that interact with microtubules are [[kinesin]], which usually moves toward the (+) end of the microtubule, and [[dynein]], which moves toward the (−) end.
* [[Dynein]] is composed of two identical heavy chains, which make up two large globular head domains, and a variable number of intermediate and light chains. Dynein-mediated transport takes place from the (+) end towards the (-) end of the microtubule.  [[Adenosine triphosphate|ATP]] hydrolysis occurs in the globular head domains, which share similarities with the AAA+ (ATPase associated with various cellular activities) protein family. ATP hydrolysis in these domains is coupled to movement along the microtubule via the microtubule-binding domains.  Dynein transports vesicles and organelles throughout the cytoplasm.  In order to do this, dynein molecules bind organelle membranes via a protein complex that contains a number of elements including [[dynactin]].
* [[Kinesin]] has a similar structure to dynein.  Kinesin is involved in the transport of a variety of intracellular cargoes, including vesicles, organelles, protein complexes, and mRNAs toward the microtubule's (+) end.<ref>{{Cite journal |vauthors=Hirokawa N, Noda Y, Tanaka Y, Niwa S |date=October 2009 |title=Kinesin superfamily motor proteins and intracellular transport |journal=Nature Reviews. Molecular Cell Biology |volume=10 |issue=10 |pages=682–96 |doi=10.1038/nrm2774 |pmid=19773780 |s2cid=18129292}}</ref>

Some viruses (including [[retroviruses]], [[herpesviridae|herpesviruses]], [[parvoviruses]], and [[adenoviruses]]) that require access to the nucleus to replicate their genomes attach to [[#Motor proteins|motor proteins]].