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Microtubule

Tubulin and Microtubule Metrics Infographic
Microtubule and tubulin metrics[1]

Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm[2] and have an inner diameter between 11 and 15 nm.[3] They are formed by the polymerization of a dimer of two globular proteins, alpha and beta tubulin into protofilaments that can then associate laterally to form a hollow tube, the microtubule.[4] The most common form of a microtubule consists of 13 protofilaments in the tubular arrangement.

Microtubules are one of the cytoskeletal filament systems in eukaryotic cells. The microtubule cytoskeleton is involved in the transport of material within cells, carried out by motor proteins that move on the surface of the microtubule.

Microtubules play an important role in a number of cellular processes. They are involved in maintaining the structure of the cell and, together with microfilaments and intermediate filaments, they form the cytoskeleton. They also make up the internal structure of cilia and flagella. They provide platforms for intracellular transport and are involved in a variety of cellular processes, including the movement of secretory vesicles, organelles, and intracellular macromolecular assemblies.[5] They are also involved in cell division (by mitosis and meiosis) and are the main constituents of mitotic spindles, which are used to pull eukaryotic chromosomes apart.

Microtubules are nucleated and organized by microtubule-organizing centres, such as the centrosome found in the center of many animal cells or the basal bodies of cilia and flagella, or the spindle pole bodies found in most fungi.

There are many proteins that bind to microtubules, including the motor proteins dynein and kinesin, microtubule-severing proteins like katanin, and other proteins important for regulating microtubule dynamics.[6] Recently an actin-like protein has been found in the gram-positive bacterium Bacillus thuringiensis, which forms a microtubule-like structure called a nanotubule, involved in plasmid segregation.[7] Other bacterial microtubules have a ring of five protofilaments.

  1. ^ "Digital Downloads". PurSolutions. Archived from the original on 2022-09-29. Retrieved 2020-02-20.
  2. ^ Ledbetter MC, Porter KR (1963). "A "microtubule" in plant cell fine structure". Journal of Cell Biology. 19 (1): 239–50. doi:10.1083/jcb.19.1.239. PMC 2106853. PMID 19866635.
  3. ^ Chalfie M, Thomson JN (1979). "Organization of neuronal microtubules in the nematode Caenorhabditis elegans". Journal of Cell Biology. 82 (1): 278–89. doi:10.1083/jcb.82.1.278. PMC 2110421. PMID 479300.
  4. ^ Diwan JJ (2006). "Microtubules". Rensselaer Polytechnic Institute. Archived from the original on 2014-02-06. Retrieved 2014-02-24.
  5. ^ Vale RD (February 2003). "The molecular motor toolbox for intracellular transport". Cell. 112 (4): 467–80. doi:10.1016/S0092-8674(03)00111-9. PMID 12600311. S2CID 15100327.
  6. ^ Howard J, Hyman AA (February 2007). "Microtubule polymerases and depolymerases". Current Opinion in Cell Biology. 19 (1): 31–5. doi:10.1016/j.ceb.2006.12.009. PMID 17184986.
  7. ^ Jiang S, Narita A, Popp D, Ghoshdastider U, Lee LJ, Srinivasan R, Balasubramanian MK, Oda T, Koh F, Larsson M, Robinson RC (March 2016). "Novel actin filaments from Bacillus thuringiensis form nanotubules for plasmid DNA segregation". Proceedings of the National Academy of Sciences of the United States of America. 113 (9): E1200-5. Bibcode:2016PNAS..113E1200J. doi:10.1073/pnas.1600129113. PMC 4780641. PMID 26873105.

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