What is a Microtubule?

A fibrous structure commonly found in eukaryotic cells, its shape is straight, its cross section is circular, and its diameter is about 22-25nm.

A fibrous structure commonly found in eukaryotic cells, its shape is straight, its cross section is circular, and its diameter is about 22-25nm.

The cortex (tube wall) of the microtubules is a collection of 13 fibril filaments, and tubulin (tubulin) is the main protein constituting the microtubules.

Chinese name

Microtubule

Foreign name

Microtubule

Make up

alpha-tubulin, beta-tubulin

Definition

A polar cytoskeleton

Microtube I. Existing form:

1. Single microtube :

It is found in microtubules scattered in the cytoplasm, which make up the mitosis, and in neurons. Most of the cytoplasmic microtubules are single microtubules. In addition to the latter, these microtubules are susceptible to depolymerization due to the effects of low temperature, Ca, and colchicine.

2. Two microtubules :

The microtubules found around the cilia or flagella are composed of two tubes (subfilaments) connected side by side. They are less sensitive to low temperature, Ca, and colchicine, but they still disaggregate when treated with ultrasound or high pressure.

3. Triple tube :

It is found in centriole and matrix, and is composed of three subfilaments connected side by side, which is the most stable.

Microtubules 2. Physiological functions:

Microtubules have the dynamic characteristics of aggregation and disaggregation, and play an important role in maintaining cell morphology, cell division, signal transduction, and material transport. Under physiological conditions, the structure of cells, the positioning and function of organelles depend on the stability of the microtubule structure. details as follows:

1. The microtubules make up the flagella and cilia, which contribute to their movement. The microtubule structure constituting the flagella and cilia is "9 + 2" type, that is, the outer periphery is composed of 9 pairs of double tubes (each pair contains an A subfilament and a B subfilament), with a pair of microtubules in the middle. There are two kinds of proteins on the double tube A subfilament-connexin and dynein. Connexin is always connected to the adjacent B subfilament, while dynein is sometimes connected to the adjacent B subfilament and sometimes separated. Dynein consists of a disc-shaped base attached to A subfilament and three soft heads containing ATP hydrolase. What causes the movement of flagella and cilia is the sliding between A and B subfilaments assisted by dynein.

2. Microtubules participate in the transmission of neurotransmitters in nerve cells, and participate in the transport of intracellular vesicles and pigments, which have a certain supporting effect on the localization of organelles such as mitochondria and ribosomes.

3. The microtubules form a spindle and play an important role in the movement of chromosomes during cell division.

4. Microtubules play a decisive role in the morphogenesis of early embryos.

5. The microtubules together with other fibers constitute the cytoskeleton. The double-helix structure of the microtubules supports the physiological form of the cell. It does not shrink itself, so it can maintain the physiological form of the cell.

6. Microtubules have the function of transmitting important information, such as microtubule signal transduction for important biological functions. Nowadays, many researches on this signal channel have been confirmed, and microtubules have been involved in protein kinase signal transduction function. After interacting with tubulin, signal molecules are further transmitted.