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Actin filaments decorated

Figure 3. Actin filaments. Electron microscope images of individual negatively stained actin filaments [left] and actin filaments decorated by myosin S1 fragments [right]. The black V shapes indicate the pointed and barbed end directions of the filaments as marked by labeling with myosin subfragment 1. Scale bars 100 nm. Images provided courtesy of Dr Roger Craig. Figure 3. Actin filaments. Electron microscope images of individual negatively stained actin filaments [left] and actin filaments decorated by myosin S1 fragments [right]. The black V shapes indicate the pointed and barbed end directions of the filaments as marked by labeling with myosin subfragment 1. Scale bars 100 nm. Images provided courtesy of Dr Roger Craig.
The myosin head has long been shown to induce, even in low ionic strength buffers, polymerization of G-actin into decorated F-actin-S i filaments that exhibit the classical arrowhead structure (Miller et al., 1988 and older references therein). However, to date, the molecular mechanism of this polymerization process remains unknown. [Pg.54]

The two ends of the F-actin filaments have different surfaces of the monomer exposed and grow at different rates. This has been demonstrated by allowing the myosin fragment called heavy meromyosin (HMM see Fig. 19-10) to bind to (or "decorate") an actin filament. The... [Pg.1098]

Without the atomic resolution afforded by x-ray crystallography, the cleft in an actin subunit and therefore the polarity of a filament are not detectable. However, the polarity of actin filaments can be demonstrated by electron microscopy in decoration experiments, which exploit the ability of myosin to bind specifically to actin filaments. In this type of experiment, an excess of myosin SI, the globular head domain of myosin, is mixed with actin filaments and binding is permitted to take place. Myosin attaches to the sides of a filament with a slight tilt. When all the actin subunits are bound by myosin, the filament appears coated ( decorated ) with arrowheads that all point toward one end of the filament (Figure 19-4). Because... [Pg.782]

A EXPERIMENTAL FIGURE 19-4 Decoration demonstrates the polarity of an actin filament. Myosin SI head domains bind to actin subunits in a particuiar orientation. When bound to aii the subunits in a fiiament, SI appears to spirai around the fiiament. This coating of myosin heads produces a series of arrowhead-iike decorations, most easiiy seen at the wide views of the fiiament. The poiarity in decoration defines a pointed (-) end and a barbed (-f) end the former corresponds to the top of the model in Figure 19-3c. [Courtesy of R. Craig.]... [Pg.782]

A EXPERIMENTAL FIGURE 19-8 Myosin decoration and capping proteins demonstrate unequal growth rates at the two ends of an actin filament, (a) When short myosindecorated filaments are the nuclei for actin polymerization, the resulting elongated filaments have a much longer undecorated (-t) end than (-) end. This result indicates that G-actin monomers are added much faster at the (-t) end than at the (-) end. [Pg.785]

Kovar, D. R. Gibbon, B. C. McCurdy, D. W. Staiger, C. J. Fluorescently-labeled fimbrin decorates a dynamic actin filament network in live plant cells. [Pg.298]

Figure Bl.17.6. A protein complex (myosin SI decorated filamentous actin) embedded in a vitrified ice layer. Shown is a defociis series at (a) 580 mn, (b) 1130 mn, (c) 1700 mn and (d) 2600 mn underfocus. The pictures result from averagmg about 100 individual images from one electron micrograph the decorated filament length shown is 76.8 nm. Figure Bl.17.6. A protein complex (myosin SI decorated filamentous actin) embedded in a vitrified ice layer. Shown is a defociis series at (a) 580 mn, (b) 1130 mn, (c) 1700 mn and (d) 2600 mn underfocus. The pictures result from averagmg about 100 individual images from one electron micrograph the decorated filament length shown is 76.8 nm.
Moore, P. B., Huxley, H. E., and De Rosier, D. J. (1970). Three-dimensional reconstruction of F-actin, thin filaments and decorated thin filaments. /. Mol. Biol. 50, 279-295. [Pg.84]

The protein myosin (Fig. 5-32) interacts specifically with each actin molecule in a filament and, as a result, the filament becomes decorated with a pattern of arrow-heads all pointing the same way. Because of this pattern, one end of the filament is known as the pointed end while the other is called the barbed end. [Pg.133]

Fig. 4. Muscle proteins. Positions of myosin heads (S-1), actin monomers (A) and troponin (circies) in active and relaxed states shown in relationship to a cross section of decorated actin. S-1 a, S-1 b and S-1 c indicate the domains of the HMM. Aa and Ab are the domains of the actin monomers. The circles labeled a" show troponin fibrils in the active position b" and "c are possible positions in the relaxed state. This drawing is not a helical projection but a schematic view of two actin monomers (the one on top is 27 A above the other one and rotated by about 167° around the filament axis) and their associated S1s. The SI on the left is therefore 27 A above the SI on the right hand side of the drawing. In three dimensions, additional S1s would be in contact with both of the actin subunits shown. Therefore it only appears in this two-dimensional drawing that the tropomyosin and SI do not make equivalent contacts with the two ac-tins. [Used with permission from E.H.Egelman J. Muse. Res. Cell. Moti7. 6(1985) 129-151]... Fig. 4. Muscle proteins. Positions of myosin heads (S-1), actin monomers (A) and troponin (circies) in active and relaxed states shown in relationship to a cross section of decorated actin. S-1 a, S-1 b and S-1 c indicate the domains of the HMM. Aa and Ab are the domains of the actin monomers. The circles labeled a" show troponin fibrils in the active position b" and "c are possible positions in the relaxed state. This drawing is not a helical projection but a schematic view of two actin monomers (the one on top is 27 A above the other one and rotated by about 167° around the filament axis) and their associated S1s. The SI on the left is therefore 27 A above the SI on the right hand side of the drawing. In three dimensions, additional S1s would be in contact with both of the actin subunits shown. Therefore it only appears in this two-dimensional drawing that the tropomyosin and SI do not make equivalent contacts with the two ac-tins. [Used with permission from E.H.Egelman J. Muse. Res. Cell. Moti7. 6(1985) 129-151]...
On stimulation, the tubules decrease in number and transform into microvilli, decorating the secretory canaliculus, which expands in surface area and volume as acid is secreted into the canalicular space. The microvilli contain actin fibers that have moved from the cytoplasm, as shown by phallucidin staining. However, the ratio of globular (G) to filamentous (F) actin stays approximately the same, suggesting that eversion of the tubules is by a process of addition of actin at the growing tip and removal of actin from the base of the tubule. [Pg.109]


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See also in sourсe #XX -- [ Pg.171 ]




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