What is a microtubule? Definition:
Under microtubules Tubules are understood to mean fine protein structures which are combined within the cell to form a tube-like system. The microtubules together with the intermediate filaments and the microfilaments form the basis for the cytoskeleton of the cell, which occurs in this form only in eukaryotes. Microtubules occur as mobile and short-lived or as stable and long-lived versions. In prokaryotes protein compounds act as a stabilizing element, but these are not directly comparable with the microtubules. The similarity of the cytoskeletons of both cell types is probably due to analogous development.
The tubular branches of microtubules are formed by globular (globular) proteins. Their size is between 15 and 25 nanometers, more than 25,000 times smaller than the cell itself. Especially in the treatment of cancer, microtubules are becoming increasingly important. Special drugs that affect the alignment of chromosomes in the division of tumor cells are already approved as cytostatic or chemotherapeutic agents.
Structure of microtubules
The basic structure of the microtubules is represented by a so-called protofilament. This consists of alpha and beta tubulin dimers, which in combination form the branched subsystems of the microtubule (protofilaments).
The typical structure of the spiral-shaped microtubules is caused by a large number of protofilaments, which also make up the characteristic structure of the hollow body. Protofilaments are composed according to the head-tail principle. This means that the protofilaments have only annular beta-tubulin segments on one side and only the alpha-tubulin units on the other side. This property is essential for an equivalent polarity of the microtubules.
Function of the microtubule
The function of the microtubules is not only based on the interactions between the tubulin units but also within the protofilaments. The tasks of the microtubules is therefore also multifunctional. In addition to influencing the correct arrangement of the chromosomes in mitosis, they also include vesicle movement in the cell. The vesicle activity is based on a "rail system" which serves as a transport prerequisite for the motor proteins and consists of the microtubules.
In addition, the microtubules on certain cell types geiЯeln or cilia for the purpose of locomotion. An impressive example of this microtubule-promoting process is the movement of sperm. The microtubules also actively participate in the process of catching the phagocytosis.