Phase diagram of microtubules.
نویسندگان
چکیده
The protein tubulin is found in every cell of every living organism (with the exception of bacteria ) [1]. In the presence of guanosine-tri-phosphate (GTP) and magnesium ions (Mg +), tubulin-GTP complexes form [2] and aggregate [3] into long, hollow cylinders called microtu bules. Microtubules are about 25 nm in outer diameter, incorporate 1625 tubulin dimers per micrometer of their length [4] and easily grow long enough to span a cell (10—100 pm). In the cell, microtubules form a network that supports the overall structure and guides internal transport [5]. Fundamental cellular processes, like locomotion, morphogenesis, and reproduction, rely on the ability of microtubules to change their organization. This ability derives from a unique feature of microtubule assembly called dynamic instability [6]. The term dynamic instability describes the fact that individual microtubules are dynamic structures that Auctuate erratically between assembling and disassembling. These Auctuations are not microscopic; they often involve most or all of the microtubule. A typical plot of the length of a single microtubule over time is shown in Fig. 1. This so-called dynamic instability depends on the hydrolysis reaction which turns the GTP of the tubulinGTP cotnplex into guanosine-di-phosphate (GDP) and releases energy (-8k T/reaction) [7]. Dynamic instability has been the subject of research for the past decade. The key element of all models is a competition between growth and the process of hydrolysis, often considered in terms of a growth front and a possible hydrolysis front. Crudely, when the hydrolysis front overtakes the growth front, the microtubule structure becomes unstable. The question of exactly how the hydrolysis and growth reactions are coupled continues to
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ورودعنوان ژورنال:
- Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics
دوره 50 2 شماره
صفحات -
تاریخ انتشار 1994