Properties of Microtubules
Microtubules are polar with a positive (+) charge at one end, and the opposite ends have negative (-) charges that grow more slowly. Protofilaments are tiny parts of microtubules that line up in a row with the positive end always showing β-subunits and the negative end showing α-subunits. The pairs of tubulins can depolymerize or break apart. Both α- and β-tubulin bind to GTP for polymerization or depolymerization. The GTP bound to β-tubulin hydrolyzes to GDP in polymerization. The change weakens the binding affinity of tubulin and results in depolymerization and the dynamic nature of microtubules.
Treadmilling
Microtubules go through a process known as treadmilling. In this process, tubulin molecules connected to GDP are continually lost from the negative end and replaced by tubulin with GTP at the positive end of the same microtubule.
Dynamic instability
When new tubulin bound to GTP adds up faster than hydrolyzation of GTP and then is changed into GDP, the microtubule holds onto a GTP cap at its plus end, causing it to grow. On the other hand, if the growth rate slows down, the GTP-bound tubulin at the plus end is replaced by GDP. This results in a rapid depolarization of the microtubule. This back-and-forth process of growth and shrinkage in microtubules is known as dynamic instability.
Microtubules: Structure & Function
Microtubules are small polymerized tubular structures made up of tubulin proteins. Microtubules, microfilaments, and intermediate filaments are the important parts of the cytoskeleton. Microtubule is an important component of cell structure in plant and animal cells. It plays a major role in the functions of a variety of processes including cell division, cell movement, maintaining cell shape, etc.
These are rigid, hollow rods made up of α-tubulin and β-tubulin proteins that create protofilaments for polar microtubule formation. There are three types of microtubules involved in mitosis, namely astral, polar, and kinetochore. Kinesin and dynein are microtubule-associated proteins that make the internal transport network of cells.
Table of Content
- What are Microtubules?
- Structure of Microtubules
- Properties of Microtubules
- Functions of Microtubules
- Types and Functions of Microtubules Associated with Mitosis
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