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Microtubules play an important role in a number of cellular processes. They are involved in maintaining the structure of the cell and, together with microfilaments and intermediate filaments, they form the cytoskeleton. They also make up the internal structure of cilia and flagella.
Eukaryotic cells contain three main kinds of cytoskeletal filaments: microfilaments, microtubules, and intermediate filaments. In neurons the intermediate filaments are known as neurofilaments. [16] Each type is formed by the polymerization of a distinct type of protein subunit and has its own characteristic shape and intracellular distribution.
The anti-parallel orientation of tetramers means that, unlike microtubules and microfilaments, which have a plus end and a minus end, IFs lack polarity and cannot serve as basis for cell motility and intracellular transport. Also, unlike actin or tubulin, intermediate filaments do not contain a binding site for a nucleoside triphosphate.
Intermediate filaments contain an average diameter of 10 nm, which is smaller than that of microtubules, but larger than that of microfilaments. [4] These 10 nm filaments are made up of polypeptide chains, which belong to the same family as intermediate filaments. Intermediate filaments are not involved with the direct movement of cells unlike ...
The eukaryotic cytoskeleton is composed of microtubules, intermediate filaments and microfilaments. In the cytoskeleton of a neuron the intermediate filaments are known as neurofilaments. There are a great number of proteins associated with them, each controlling a cell's structure by directing, bundling, and aligning filaments. [2]
Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin , but are modified by and interact with numerous other proteins in the cell.
In cell biology, microtubule nucleation is the event that initiates de novo formation of microtubules (MTs). These filaments of the cytoskeleton typically form through polymerization of α- and β-tubulin dimers, the basic building blocks of the microtubule, which initially interact to nucleate a seed from which the filament elongates.
Microtubules are assembled from dimers of α- and β-tubulin. These subunits are slightly acidic, with an isoelectric point between 5.2 and 5.8. [14] Each has a molecular weight of approximately 50 kDa. [15] To form microtubules, the dimers of α- and β-tubulin bind to GTP and assemble onto the (+) ends of microtubules while in the GTP-bound ...