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Encyclopedia > Cytoskeleton
The eukaryotic cytoskeleton. Actin filaments are shown in red, microtubules in green, and the nuclei are in blue.
The eukaryotic cytoskeleton. Actin filaments are shown in red, microtubules in green, and the nuclei are in blue.

The cytoskeleton is a cellular "scaffolding" or "skeleton" contained within the cytoplasm. The cytoskeleton is present in all cells; it was once thought this structure was unique to eukaryotes, but recent research has identified the prokaryotic cytoskeleton. It is a dynamic structure that maintains cell shape, and also has been known to protect the cell, enables cellular motion (using structures such as flagella, cilia and lamellipodia), and plays important roles in both intracellular transport (the movement of vesicles and organelles, for example) and cellular division. Image File history File links FluorescentCells. ... Image File history File links FluorescentCells. ... This article is about the temporary framework. ... For other uses, see Skeleton (disambiguation). ... Cross section of cell with cytoplasm labeled at center right. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... Elements of the Caulobacter crescentus cytoskeleton. ... For the insect anatomical structure, see Antenna (biology). ... Not to be confused with Psyllium. ... A GFP label of the actin cytoskeleton in a melanoma cell, showing a ruffled-edge lamellipodium, from Cell Biology at IMB Salzburg. ... In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. ... This does not adequately cite its references or sources. ...

Contents

The eukaryotic cytoskeleton

Actin cytoskeleton of mouse embryo fibroblasts, stained with phalloidin
Actin cytoskeleton of mouse embryo fibroblasts, stained with phalloidin

Eukaryotic cells contain these main kinds of cytoskeletal filaments. The cytoskeleton provides the cell's cytoplasm with structure and shape. Image File history File links MEF_microfilaments. ... Image File history File links MEF_microfilaments. ... Binomial name Mus musculus Linnaeus, 1758 Mus musculus is the common house mouse. ... For other uses, see Embryo (disambiguation). ... NIH/3T3 Fibroblasts A fibroblast is a type of cell that synthesizes and maintains the extracellular matrix of many animal tissues. ... Phalloidin is a toxin from the death cap mushroom Amanita phalloides that binds actin, preventing its depolymerization and poisoning the cell. ... Kingdoms Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. ...


Actin filaments / Microfilaments

Main article: actin

Around 7 nm in diameter, this filament is composed of two intertwined actin chains. Microfilaments are most concentrated just beneath the cell membrane, and are responsible for resisting tension and maintaining cellular shape, forming cytoplasmatic protuberances (like pseudopodia and microvilli- although these by different mechanisms), and participation in some cell-to-cell or cell-to-matrix junctions. In association with these latter roles, microfilaments are essential to transduction. They are also important for cytokinesis (specifically, formation of the cleavage furrow) and, along with myosin, muscular contraction. Actin/Myosin interactions also help produce cytoplasmic streaming in most cells. G-Actin (PDB code: 1j6z). ... Look up cell membrane in Wiktionary, the free dictionary. ... Pseudopods or pseudopodia (false feet) are temporary projections of eukaryotic cells. ... The microvilli (singular: microvillus) are structures that increase the surface area of cells by approximately 600 fold (human), thus facilitating absorption and secretion. ... In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes and linked through second messengers resulting in what is thought of as... A cell that has almost completed cytokinesis. ... In cell biology, the cleavage furrow is the indentation that begins the process of cleavage, by which animal cells undergo cytokinesis. ... Myosin is a motor protein filament found in muscle tissue. ... A top-down view of skeletal muscle Skeletal muscle is a type of striated muscle, usually attached to the skeleton. ... G-Actin (PDB code: 1j6z). ... Myosin is a motor protein filament found in muscle tissue. ... Cytoplasmic streaming is the flowing of cytoplasm in eukaryotic cells. ...


Intermediate filaments

Microscopy of keratin filaments inside cells.
Microscopy of keratin filaments inside cells.
Main article: intermediate filament

These filaments, 8 to 12 nanometers in diameter, are more stable (strongly bound) than actin filaments, and heterogeneous constituents of the cytoskeleton. Like actin filaments, they function in the maintenance of cell-shape by bearing tension (microtubules, by contrast, resist compression. It may be useful to think of micro- and intermediate filaments as cables, and of microtubules as cellular support beams). Intermediate filaments organize the internal tridimensional structure of the cell, anchoring organelles and serving as structural components of the nuclear lamina and sarcomeres. They also participate in some cell-cell and cell-matrix junctions. Image File history File links KeratinF9. ... Image File history File links KeratinF9. ... // Intermediate filaments (IFs) are important structural proteins which are located both in the cytoplasm and the nucleus. ... Microtubules are protein structures found within cells. ... The nuclear lamina is a dense, ~ 30 to 100 nanometers thick, fibrillar network composed of intermediate filaments made of lamin that lines the inner surface of the nuclear envelope in animal cells. ... Image of sarcomere A sarcomere is the basic unit of a cross striated muscles myofibril. ...


Different intermediate filaments are:

Introduction Vimentin is part of the intermediate filament family. ... Not to be confused with kerogen or carotene. ... For other uses, see Skin (disambiguation). ... For the 1968 stage production, see Hair (musical), for the 1979 film, see Hair (film). ... For other uses, see Nail. ... Intermediate filaments are one component of the cytoskeleton - important structural components of living cells. ... A lamin is a fibrous protein that gives the cell nucleus its shape. ...

Microtubules

Microtubules in a gel fixated cell.
Main article: microtubule

Microtubules are hollow cylinders of about 25 nm in diameter (lumen = approximately 15nm in diameter), most commonly comprised of 13 protofilaments which, in turn, are polymers of alpha and beta tubulin. They have a very dynamic behaviour, binding GTP for polymerization. They are commonly organized by the centrosome. Image File history File linksMetadata Download high resolution version (779x695, 251 KB) Summary This image has been taken from the Dutch Wikipedia: http://nl. ... Image File history File linksMetadata Download high resolution version (779x695, 251 KB) Summary This image has been taken from the Dutch Wikipedia: http://nl. ... Image File history File links Animal_cell_structure. ... Image File history File links Animal_cell_structure. ... Microtubules are one of the components of the cytoskeleton. ... Tubulin is the protein which makes up microtubules. ... Guanosine triphosphate (GTP) is also known as guanosine-5-triphosphate. ... The centrosome is the main microtubule organizing center (MTOC) of the cell as well as a regulator of cell-cycle progression. ...


In nine triplet sets (star-shaped), they form the centrioles, and in nine doublets oriented about two additional microtubules (wheel-shaped) they form cilia and flagella. The latter formation is commonly referred-to as a "9+2" arrangement, wherein each doublet is connected to another by the protein dynein. A centriole in biology is a hollow cylindrical organelle found in most animal cells, and cells of fungi and algae though not frequently in plants. ... Dynein is a motor protein (also called molecular motor or motor molecule) in cells which converts the chemical energy contained in ATP into the mechanical energy of movement. ...


They play key roles in:

An eighth eukaryotic cytoskeletal element, microtrabeculae, were proposed by Keith Porter in the 1960s. Porter's lab observed short, filamentous structures of unknown molecular composition in electron micrographs of whole cells. Due to their filamentous appearance and association with known cytoplasmic structures, microtrabeculae were speculated to represent a novel filamentous network distinct from microtubules, filamentous actin, or intermediate filaments. However, they were later shown by Hans Ris and others to be an artifact of certain types of fixation treatment. Dynein is a motor protein (also called molecular motor or motor molecule) in cells which converts the chemical energy contained in ATP into the mechanical energy of movement. ... The kinesin dimer attaches to, and moves along, microtubules. ... In cell biology, an organelle is one of several structures with specialized functions, suspended in the cytoplasm of a eukaryotic cell. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. ... An axoneme is the core scaffold of the eukaryotic cilia and flagella, which are projections from the cell made up of microtubules. ... Not to be confused with Psyllium. ... For the insect anatomical structure, see Antenna (biology). ... Micrograph showing condensed chromosomes in blue and the mitotic spindle in green during prometaphase of mitosis The mitotic spindle (a. ...


The prokaryotic cytoskeleton

Main article: prokaryotic cytoskeleton

The cytoskeleton was previously thought to be a feature only of eukaryotic cells, but homologues to all the major proteins of the eukaryotic cytoskeleton have recently been found in prokaryotes.[1] Although the evolutionary relationships are so distant that they are not obvious from protein sequence comparisons alone, the similarity of their three-dimensional structures and similar functions in maintaining cell shape and polarity provides strong evidence that the eukaryotic and prokaryotic cytoskeletons are truly homologous.[2] Elements of the Caulobacter crescentus cytoskeleton. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... In biology, homology is any similarity between structures that is due to their shared ancestry. ... Prokaryotes are unicellular (in rare cases, multicellular) organisms without a nucleus. ... Proteins are an important class of biological macromolecules present in all biological organisms, made up of such elements as carbon, hydrogen, nitrogen, oxygen, and sulfur. ...


FtsZ

FtsZ was the first protein of the prokaryotic cytoskeleton to be identified. Like tubulin, FtsZ forms filaments in the presence of GTP, but these filaments do not group into tubules. During cell division, FtsZ is the first protein to move to the division site, and is essential for recruiting other proteins that synthesize the new cell wall between the dividing cells. FtsZ is a protein encoded by the ftsZ gene that assembles into a ring at the future site of the septum of bacterial cell division. ... Guanosine triphosphate (GTP) is also known as guanosine-5-triphosphate. ... This does not adequately cite its references or sources. ... Plant cells separated by transparent cell walls. ...


MreB and ParM

Prokaryotic actin-like proteins, such as MreB, are involved in the maintenance of cell shape. All non-spherical bacteria have genes encoding actin-like proteins, and these proteins form a helical network beneath the cell membrane that guides the proteins involved in cell wall biosynthesis. MreB is a protein found in bacteria that has been identified as a homologue of actin. ... For other uses, see Gene (disambiguation). ... Biosynthesis is a phenomenon where chemical compounds are produced from simpler reagents. ...


Some plasmids encode a partitioning system that involves an actin-like protein ParM. Filaments of ParM exhibit dynamic instability, and may partition plasmid DNA into the dividing daughter cells by a mechanism analogous to that used by microtubules during eukaryotic mitosis. Figure 1: Illustration of a bacterium with plasmids enclosed showing chromosomal DNA and plasmids. ... Microtubules are protein structures found within cells, one of the components of the cytoskeleton. ... The wings of pterosaurs (1), bats (2) and birds (3) are analogous: they serve the same function and are similar in structure, but each evolved independently. ... Mitosis divides genetic information during cell division. ...


Crescentin

The bacterium Caulobacter crescentus contains a third protein, crescentin, that is related to the intermediate filaments of eukaryotic cells. Crescentin is also involved in maintaining cell shape, but the mechanism by which it does this is currently unclear. Binomial name Caulobacter crescentus Poindexter 1964 Caulobacter crescentus is a Gram-negative, oligotrophic bacterium widely distributed in aquatic environments. ... The crescentin protein is a bacterial relative of the intermediate filaments found in eukaryotic cells. ...


References

  1. ^ Shih YL, Rothfield L (2006). "The bacterial cytoskeleton". Microbiol. Mol. Biol. Rev. 70 (3): 729–54. PMID 16959967. 
  2. ^ Michie KA, Löwe J (2006). "Dynamic filaments of the bacterial cytoskeleton". Annu. Rev. Biochem. 75: 467–92. PMID 16756499. 

Further reading

  • Linda A. Amos and W. Gradshaw Amos, Molecules of the Cytoskeletion, Guilford, ISBN 0-89862-404-5, LoC QP552.C96A46 1991

External links


  Results from FactBites:
 
Cytoskeleton (211 words)
Cytoskeleton is a form of rigid structure or scaffolding contained within the cytoplasm, and necessary for cellular structure, motion and cell division.
In the eukaryotic cell, the cytoskeleton is made up primarily of actin filaments, which are about 7 nanometers (nm) in diameter; of intermediate filaments, about 8-11 nm in diameter; and microtubules, which are more complex structures.
Molecules of the Cytoskeleton by Amos & Amos
Cytoskeleton (163 words)
The cytoskeleton is a series of intercellular proteins that help a cell with shape, support, and movement.
Cytoskeleton has three main structural components: microfilaments, intermediate filaments, and microtubules.
The cytoskeleton mediates movement by helping the cell move in its environment and mediating the movement of the cell's components.
  More results at FactBites »

 
 

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