Navigation Links
Cytoskeleton


The cytoskeleton is a cellular "scaffolding" or "skeleton" contained, as all other organelles, within the cytoplasm. It is a dynamic structure that maintains cell shape, enables some cell motion (using structures such as flagella and cilia), and plays important roles in both intra-cellular transport (the movement of vesicles and organelles, for example) and cellular division.

Contents

The eukaryotic cytoskeleton

Eukaryotic cells contain three kinds of cytoskeletal filaments.

Actin Filaments

Main article: microfilaments.

Around 7 nm. in diameter, this filament is composed of two actin chains oriented in an helicoidal shape. They are mostly concentrated just beneath the plasma membrane, as they keep cellular shape, form cytoplasmatic protuberancies (like pseudopods and microvillus), participate in some cell-to-cell or cell-to-matrix junctions and the transduction of signals. They are also important for cytokinesis and, along with myosin, muscular contraction.

Intermediate Filaments

Main article: intermediate filaments

These 8 to 11 nanometers in diameter filaments are the more stable (strongly bound) and heterogenous constitutents of the cytoskeleton. They organize the internal tridimensional structure of the cell (they are structural components of the nuclear envelope or the sarcomeres for example). They also participate in some cell-cell and cell-matrix junctions.

Different intermediate filaments are:

Microtubules

Main article: microtubules

They are hollow cylinders of about 25 nm., formed by 13 protofilaments which, in turn, are polymers of alpha and beta tubulin. They have a very dynamic behaviour, binding GTP for polymerization, they are organized by the centrosome.

They play key roles in:

The prokaryotic cytoskeleton

The cytoskeleton was previously considered to be a feature only of eukaryotic cells, but recent research has revealed that homologues to all the major proteins of the eukaryotic cytoskeleton can also be found in prokaryotes. Although the evolutionary relationships are so distant that they are not obvious from protein sequence comparisons alone, the similarity of their three-dimensional structures provides strong evidence that the eukaryotic and prokaryotic cytoskeletons are truly homologous.

FtsZ

FtsZ, a relative of the eukaryotic tubulin, 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 produce a new cell wall between the dividing cells.

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.

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.

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.

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


'"/>


(Date:12/17/2014)... , Dec. 15, 2014 Research and Markets ... addition of the "Samsung Galaxy S5 - ... report to their offering. ... totally different sensing technology than the iPhone 5S, ... sensor in its product. The Galaxy ...
(Date:12/17/2014)... , Dec. 16, 2014  Automation is fundamentally ... more evident than at international borders. Over the ... scanners have allowed veteran travelers to self process ... Control (APC) Kiosks at an increasing number of ... According to Maxine Most ...
(Date:12/11/2014)... PAUL, Minn. , Dec. 10, 2014 /PRNewswire/ ... wireless physiologic monitoring, has released a new series ... needs of preclinical toxicology researchers. M series, part ... help toxicologists collect the best possible physiologic data ... Adding functional endpoints to toxicology studies ...
Breaking Biology News(10 mins):Samsung Galaxy S5 - Home Button Synaptics Fingerprint Sensor Technology Analysis 2Automated Border Control (ABC) Transforms the Global Travel Experience With More Than 2500 ABC eGates and APC Kiosks Deployed In Airports, Seaports, and Land Borders Worldwide 2New telemetry implants expected to change how large animal toxicology studies are conducted 2
... in <A HREF=",http://chinese.eurekalert.org/zh/pub_releases/2009-05/sfeb-cai052609.php,">Chinese . Researchers ... expression of a form of cytochrome P-450 (CYP4B1) ... in mice by caffeic acid, an anti-inflammatory antioxidant ... which appear in the June 2009 issue of ...
... a soldier is wounded during combat, surgeons must focus ... Technologies that could improve the repair and regeneration processes ... but they are not being moved quickly enough into ... Georgia Tech Center for Advanced Bioengineering for Soldier Survivability ...
... by millions worldwide to effectively lower blood cholesterol levels, ... (MS) patients treated with high daily dosages. A ... (MNI), McGill University, demonstrates that statin therapy in mice ... system. The findings, published in The American Journal ...
Cached Biology News:Caffeic acid inhibits colitis in a mouse model -- is a drug-metabolizing gene crucial? 2New center at Georgia Tech aims to improve recovery of soldiers with severe injuries 2New center at Georgia Tech aims to improve recovery of soldiers with severe injuries 3One size does not fit all 2
Other biology definitionOther Tags