10.5 assembly and disassembly of cytoskeleton Assembly: In two distinct phases: slower nucleation and rapid elongation The factors influencing assemble:, associated protein, MAPS; Caf, Mg, ATP, GTP Treadmilling model Cytoskeleton drugs
10.5 assembly and disassembly of cytoskeleton Assembly : In two distinct phases: slower nucleation and rapid elongation The factors influencing assemble:, associated protein, MAPs; Ca2+, Mg; ATP, GTP Treadmilling model. Cytoskeleton drugs
Nucleus Monomer ATP Filament =”浸费 iol bin F.2.1
Figure 9.49 Actin assembly in vitro. (a)Electron micro- graph of a short actin filament that was labeled with S1 myosin and then used to nucleate actin polymerization. The addition of actin subunits occurs much more rapidly at the barbed (plus)end than at the pointed (minus)end of the ex- isting filament. (b) Schematic diagram of the preferential ad dition of actin subunits at the plus end of a microfilament and their preferential loss from the minus end in an in vitro assay. As a result, subunits treadmill through the filament in vitro. (a: Courtesy of M. S. Runge and T. D. Pollard
762 CHAPTTR Is Cell Motility and Shape I Microfilaments Nucleus Nucleus Nucleus actin G-actin 9t-)end 1) endl N Steady state A FIGURE 18-11 The three phases of G-actin
it) ← Nucleation→- Elongati+ sTeady state s nuclei Time Filament Is Monomer G Actin concentration ncentration r ii·n g
(: Capping protein ce=cr Capping protoin C 2 GG-actin concentration >L 8一
ADPATP actin with actin with bound ADP bound ATP
●o Whole cilium 8 ontains axonemes with Pellet Supernal (contains axoneme (contains outer with missing outer Incubate with EDTA 8 supernatant Pellet (contains outer fibers) in presence of Me' 8 m activity is present oluble fraction Figure 9.38 Steps in the chemical dissection of cilia
tubulin molecule C with bound GTP GTP tubulin molecules a protofilaments containing GDP add to end of microtubule tubulin are unstable and peel away from the microtubule wall addition proceeds faster GDP tubulin is released than GTP hydrolysis to the cytosol 翻鞲、` tubulin molecule with bound GDP GTP cap GROWING MICROTUBULE SHRINKING MICROTUBULE
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