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6.8.1. Microfilaments or actin filaments

Microfilaments or actin filaments

Structure and composition of microfilaments

Microfilaments are the finest filaments. They are thin and flexible fibers formed by the actin protein.

Actin filaments are the main components of the cytoskeleton of muscle cells, although they are not exclusive to them.

In addition to the actin protein, microfilaments have other associated proteins:

  • Structural proteins. They join several actin filaments into bundles.
  • Regulatory proteins. For example, myosin, which together with actin intervenes in muscle contraction.

Microfilament functions

Some of its functions are the following:

  • It is involved, together with myosin, in the process of muscle contraction .
  • They provide mechanical rigidity. It forms a network under the plasma membrane, the cell cortex, responsible for the maintenance of cell shape and protein displacement.
  • They intervene, with myosin, in cell division, forming the contractile ring that separates the two daughter cells.
  • They are involved in cellular locomotion, forming actin filaments in pseudopods, typical of cells such as amoeba and white blood cells.
  • They produce cytoplasmic currents. The actin causes the cytosol pass state of gel to sol.
  • They are involved in the transport of membrane vesicles, forming endo and exocytosis vesicles, and in the transport of organelles.