Intermediate Filaments

Filamen intermediat

9.4 Intermediate Filaments (1)Intermediate filaments (IFs) heterogeneous group of proteins, divided into five major classes.IFs classes IIV are used in the construction of filaments; type V (lamins) are present in the inner lining of the nucleus.

Intermediate FilamentsTypes and Functions of IFsIFs containing keratin form the protective barrier of the skin, and epithelial cells of liver and pancreas.IFs include neurofilaments, which are the major component of the network supporting neurons.

Intermediate filaments can go through cell-cell junction via desmosome to make cell linked together, very common in epidermal cells.DesmosomeIntermediate filaments

The name intermediate filament was established because these filaments were intermediate in size between microtubules and actin filaments (average size 10 nanometers).

Intermediate FilamentsIF AssemblyAssembly:Basic building block is a rod-like tetramer formed by two antiparallel dimers.Both the tetramer and the IF lack polarity.IFs are less sensitive to chemical agents than other types of cytoskeletal elements.

Fig. 9.41 A model for intermediate filament assembly and architectureA model for intermediate filament assembly and architectureEach monomer has a pair of globular terminal domains separated by a long "-helical region (step1). Pairs of monomers associate in parallel orientation with their ends aligned to form dimers (step 2). Depending on the type of intermediate filament, the dimers may be composed of identical monomers (homodimers) or nonidentical monomers (heterodimers). Dimers in turn associate in an antiparallel, staggered fashion to form tetramers (step 3), which are thought to be the basic subunit in the assembly of intermediate filaments. The organization of the tetrameric subunits within the filament is shown in step 4. Antiparallel, staggered fashion to form tetramers

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