Profilin is an actin-binding protein involved in providing dynamic instability and restructuring of the actin cytoskeleton .
Profilin is found in all eukaryotic organisms in most cells. Profilin is important for the spatial and temporal control of the growth of actin filaments, which is a natural process during cell movement and change in cell shape. This restructuring of the actin cytoskeleton accompanies such processes as organ development, wound healing and the destruction of infectious agents by cells of the immune system . Profilin also binds proline - rich sequences in various proteins. Despite the fact that most of the profilin is associated with actin, he still has more than 50 binding partners, many of whom are related to actin. Profilin is also involved in processes occurring in the cell nucleus , such as mRNA splicing [1] Profilin binds certain types of membrane phospholipids (phosphatidylinositol 4,5-bisphosphate and inositol triphosphate). The function of these interactions is to maintain the profile in an inactive form. It can be activated by the action of the phospholipase C enzyme. Profilin is the main allergen contained in pollen of birch and many herbaceous plants.
Content
Profiling Sources and Distribution
Profilin is a protein with a molecular weight of 14-16 kDa. The only profilin gene is found in yeast, insects, and worms, and several genes are found in many other organisms, including plants. In mammalian cells, 4 isoforms of profilin were discovered, of which profilin-I is present in many tissues, while profilin-II predominates in the brain and kidneys [2]
Profilin in the regulation of actin dynamics
Profilin enhances the growth of actin microfilaments in two ways:
- Profilin binds to monomeric actin, occupying the actin-actin contacting side; thus, profilin reduces the pool of actin monomers that can be polymerized. However, profilin also catalyzes the exchange of actin-bound ADP to ATP , converting the hard-polymerizable ADP-linked actin monomers to the easily-polymerizable ATP-bound actin monomers. In addition, profilin has a greater affinity for ATP-than with ADP-linked actin monomers. Therefore, in a mixture of actin, profilin and nucleotides (ATP and ATP), actin will polymerize in a certain amount, which can be calculated according to the law of effective masses .
- Profilin-actin complexes are incorporated into growing actin polymers due to proteins such as formin - the Wiskott-Aldrich syndrome protein and VASP (all of them contain rich proline FH-2 domains). The polymerization of actin with these proteins is much faster than without their participation. Profilin is necessary for such rapid polymerization, since it provides the binding of actin monomers to proline-rich proteins. Profilin is one of the most common proteins that bind actin monomers. Proteins such as CAP and (in mammals ) thymosinΞ²4 have some functional similarities with profilin. On the other hand, ADF / cofilins can slow down and prevent the action of profilin.
Profile Opening History
Profilin was first described by Uno Lindberg and his associates in the early 1970s as a protein that binds actin monomers. [3] This happened after realizing the fact that not only in muscle, but also in non-muscle cells, actin is present in large quantities, although often in an unpolymerized state. Then the opinion arose that profilin isolates actin monomers (holds them in the form of pro-filaments) and releases them after a signal that allows you to start the rapid assembly of actin monomers into filaments.
Links
- β ^ A. (2000), Journal of Cell Science 113 (21): 3795β3803, http://jcs.biologists.org/cgi/reprint/113/21/3795.pdf , retrieved 2009-04-09
- β ^ Witke, W., Podtelejnikov, A., Di Nardo, A., Sutherland, J., Gurniak, C., Dotti, C., and M. Mann (1998) In Mouse Brain Profilin I and Profilin II Associate With Regulators of the Endocytic Pathway and Actin Assembly. The EMBO Journal 17 (4): 967-976 Entrez Pubmed 9463375
- β ^ Carlsson L, NystrΓΆm LE, Sundkvist I, Markey F, Lindberg U. (1977) Actin polymerizability is influenced by profilin, a low molecular weight protein in non-muscle cells. J. Mol. Biol. 115: 465-483 Entrez Pubmed 563468