Actin Nucleation by Formin Protein

Actin is a family of globular multi-functional proteins that form microfilaments.
An actin protein is the monomeric subunit of two types of filaments in cells: microfilaments, one of the three major components of the cytoskeleton, and thin filaments, part of the contractile apparatus in muscle cells. It can be present as either a free monomer called G-actin (globular) or as part of a linear polymer microfilament called F-actin (filamentous), both of which are essential for such important cellular functions as the mobility and contraction of cells during cell division.

Nucleating factors are necessary to stimulate actin polymerization. One such nucleating factor is the Arp2/3 complex, which mimics a G-actin dimer in order to stimulate the nucleation (or formation of the first trimer) of monomeric G-actin. The Arp2/3 complex binds to actin filaments at 70 degrees to form new actin branches off existing actin filaments. Arp2/3-mediated nucleation is necessary for directed cell migration.Also, actin filaments themselves bind ATP, and hydrolysis of this ATP stimulates destabilization of the polymer.
The growth of actin filaments can be regulated by thymosin and profilin. Thymosin binds to G-actin to buffer the polymerizing process, while profilin binds to G-actin to exchange ADP for ATP, promoting the monomeric addition to the barbed, plus end of F-actin filaments.

Formins (formin homology proteins) are a group of proteins that are involved in the polymerization of actin and associate with the fast-growing end (barbed end) of actin filaments.Most formins are Rho-GTPase effector proteins. Formins regulate the actin and microtubule cytoskeleton and are involved in various cellular functions such as cell polarity, cytokinesis, cell migration and SRF transcriptional activity.Formins are multidomain proteins that interact with diverse signalling molecules and cytoskeletal proteins, although some formins have been assigned functions within the nucleus.

[yogeshmishra]

Very useful explained in very systematic and simple manner thankYou

[nifatjan]

Nyc to see ua vedios after a long duration....were missing ua

[mrscientific]

Wow, , , it's amazing siR, , , thnks

[Wanderer-vo]

Here you are saying, formin itself is a dimer. But in Lodish... it's given that FH1 and FH2 are two adjacent domains of formin protein. Two FH2 domains from two individual formin monomers associate to form doughnut shaped FH2 dimer....
Plz clarify