A-motility

Proteins can be broadly classified into fibrous and globular. Many fibrous proteins serve a stmctural role (11). CC-Keratin has been described. Fibroin, the primary protein in silk, has -sheets packed one on top of another. CoUagen, found in connective tissue, has a triple-hehcal stmcture. Other fibrous proteins have a motile function. Skeletal muscle fibers are made up of thick filaments consisting of the protein myosin, and thin filaments consisting of actin, troponin, and tropomyosin. Muscle contraction is achieved when these filaments sHde past each other. Microtubules and flagellin are proteins responsible for the motion of ciUa and bacterial dageUa. 

The processes of meiosis and mitosis involve many motile events, from the separation of the daughter chromosomes to the final act of cell separation at cytokinesis (Wadsworth, 1993). DNA replication itself may be considered as a motile event, because the polymerase complex moves along the linear DNA. One of the most obvious motile events is the separation of the chromosomes along the mitotic spindle at anaphase. Details of the structure and polarity of microtubules in the spindle apparatus in meiosis and mitosis are known through electron and light microscopy, but it is not yet clear whether the chromosomes are pushed, pulled or... 

Rees B, Shepherd VA, Ashford AE. Presence of a motile tubular vacuole system in different phyla of fungi. Mycol Res 1994 98 985-992. 

Allelopathic Effects of A. flos-aquae on a Motile Alga... 

Actin filaments grow rapidly within cells, and the clearest evidence of this rapid growth is the ability of the cell s leading edge to move at rates of 0.5 to 1 micrometer per second. Likewise, actin-based motility of Listeria and Shigella can attain rates of nearly 0.5 micrometers per second. Because microfilaments contain about 360 actin monomers per micrometer of length, a motility rate of 0.5 to 1 micrometer per second corresponds to an apparent first-order rate constant (/.e., / apparent = on [Actin-ATP]) of about 180-360 s . The bimolecular rate constant for actin-ATP addition to the barbed end has a nominal value of 2-3 X 10 s . Therefore, one can estimate... 

In tumor progression, the acquisition of a motile/migratory phenotype is a process that generally coincides with the switch to a malignant phase. This is achieved either by local invasion/infiltration... 

Although they share some characteristics with animals and plants, the fungi are phyllogenetically distinct. Fungi are nucleated and possess well-defined cell walls but they are spore-bearing and do not photo-synthesise. They reproduce asexually or sexually and usually exhibit filamentous growth but some have life cycles that are characterised by the inclusion of a motile, free swimming phase. 

Bacteria also contain filamentous proteins that resemble F-actin and which may be utilized for cell-shape determination 301c Actin-based motility is used by some bacteria and other pathogens during invasion of host cells (Box 19-C). It is employed by sperm cells of Ascaris and of C. elegans, which crawl by an ameboid movement that utilizes treadmilling of filaments formed from a motile sperm protein, which does not... 

Silicon tetrachloride is a motile, colourless or light yellow liquid (the boiling point is 57.7 °C) with a pungent odour. It is soluble in dichloro-ethane, gasoline and other organic solvents. It combines with alcohols to form ethers of orthosilicon acid. It strongly fumes in air, because humidity hydrolyses it and releases hydrogen chloride vapours. 

The second set of experiments used exuded cytoplasm from Chara. Here, streaming was totally inhibited by the addition of CB, and although the fibrils were still present, their motility was significantly reduced relative to controls. Notably, Characean microfilaments are uncharacteristic in that they are operationally different.41 They fail to shorten to change cell morphology but give rise to a motile force that is parallel to their surface, thereby creating movement.43... 

A motility test is usefrd because B. anthracis is a nomnotile bacterium. Two motihty tests available are the wet mount and motihty medium variety. In a wet-mount preparation, organisms with Brownian movement or no movement will support the presence of B. anthracis. The presence of B. anthracis in a motdity medium preparation would be a single line of growth along the original inoculum stab (CDC, ASM, APHL, 2002). 

Palenik, B. and others (2003). The genome of a motile marine Synechococcus. Nature 424, 1037—1042. 

Dawes AT, Edelstein-Keshet L. Phosphoinositides and Rho proteins spatially regulate actin polymerization to initiate and maintain directed movement in a one-dimensional model of a motile ceU. Biophys. J. 2646 92 744-768. 

RLC phosphorylation also causes myosin to move actin filaments in a motility assay. Dephosphorylated extended myosin adhered to a nitrocellulose substratum does not support movement of actin fila-... 

Calponin" Actin Myosin Tropomyosin V max (%) (%) ratio CP/A motility (pM CP) Reference... 

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