What Are Intermediate Filaments?

It is widely found in eukaryotic cells. It was first found in smooth muscle cells. It is named "intermediate" because it is between the actin filaments and myosin thick filaments in muscle cells. Intermediate fibers are the most complex of the three types of framework fibers. Treatment with concentrated salt solution and non-ionic detergent can make most of the rest of the cytoskeleton in the cell disappear. Only the intermediate fibers are retained. It can be seen that the intermediate fibers are the toughest and durable in the three types of cytoskeleton.

Intermediate fiber

Intermediate fibers are also called intermediate filaments (IF) with a diameter of about 10 nm, which is between thick muscle filaments and

(Intermediate filaments)

Compared with microtubules and microfilaments, the intermediate fibers have at least three differences in structure and function. First of all, the intermediate fibers are quite stable. Even if cells are extracted with detergent and high-salt solutions, the intermediate fibers remain intact. Second, the intermediate fibers are different in volume from the microtubes and microwires. The diameter of the microtubes is 24nm, the microwires are 7nm, and the intermediate fibers are 10nm. And the morphology is also different. The microtubules are hollow tubular structures assembled from tubulin dimers. The microfilaments are -helical fibers assembled from spherical subunits, and the subunits of the intermediate fibers are -helical rods. It is assembled into a rod-like structure. Third, the subunits of IF do not bind to different nucleotides, the subunits of microtubules bind to GTP or GDP, and the subunits of microfilaments bind to ATP or ADP. But many details about the assembly of intermediate fibers are unclear.