actin-binding-proteins



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To read more about the role of actin binding proteins in actin filament crosslinking see:

Crosslinkers and Actin

To read more about the role of actin binding proteins in actin treadmilling see:

Actin Treadmilling

Glossary Term: Actin Binding Proteins

Proteins that bind to actin filaments direct the location, rate, and timing of actin filament assembly and disassembly (see panels A, B, D, E in bottom Figure). Actin filaments are also stabilized (see figure “Tropomyosin stabilizes thin filaments“) and crosslinked by actin binding proteins; the specific type of crosslinking protein influences not only the type of structure the actin filaments form, but the crosslinking proteins also modulate the physical dynamics of the network (reviewed in [1, 2, 3]). Proteins with similar functions (e.g. fascin, α-actinin) act cooperatively to enhance the mechanical integrity and responsiveness of the network [4] (reviewed in [5]).

There is great structural diversity in the types of proteins which bind to actin, but the actin binding domains (ABD) themselves can be grouped according to the conserved structures they form (reviewed in [6]). Examples of ABDs mentioned throughout this resource include:

Figure: Types of actin filament crosslinking proteins. Smaller cross-linking proteins that are more globular (e.g. fascin) or have more than one actin binding site (e.g. fimbrin, α-actinin dimers) primarily form actin bundles. Larger crosslinking proteins (e.g. spectrin, filamin, dystrophin) create more space between actin filaments and they generally form actin networks. Other actin crosslinking proteins not shown here include: scruin, dematin, and villin.

Figure: Actin binding proteins influence actin dynamics. A. Treadmilling of actin filaments can be altered by profilin and ADF which generally increase and decrease the size of actin filaments, respectively. B. New filaments are nucleated by the ARP2/3 complex, which binds both G-actin monomers and the side of actin filaments to nucleate new filaments or branches. Formins nucleate new filaments by binding G-actin and through cooperation with profilin. C. Actin cross-linking proteins influence the packing and organization of actin filaments into secondary structures. D. Capping and severing proteins promote disassembly of actin filaments. E. Actin filament assembly can be modulated by events such as controlled nucleotide hydrolysis (e.g. ATP on actin) and reversible modifications (e.g. phosphorylation) on components that control actin assembly.

References

  1. Revenu C., Athman R., Robine S. & Louvard D. The co-workers of actin filaments: from cell structures to signals. Nat. Rev. Mol. Cell Biol. 2004; 5(8):635-46. [PMID: 15366707]
  2. Paavilainen VO., Bertling E., Falck S. & Lappalainen P. Regulation of cytoskeletal dynamics by actin-monomer-binding proteins. Trends Cell Biol. 2004; 14(7):386-94. [PMID: 15246432]
  3. Insall RH. & Machesky LM. Actin dynamics at the leading edge: from simple machinery to complex networks. Dev. Cell 2009; 17(3):310-22. [PMID: 19758556]
  4. Tseng Y., Kole TP., Lee JS., Fedorov E., Almo SC., Schafer BW. & Wirtz D. How actin crosslinking and bundling proteins cooperate to generate an enhanced cell mechanical response. Biochem. Biophys. Res. Commun. 2005; 334(1):183-92. [PMID: 15992772]
  5. Carlier MF. & Pantaloni D. Control of actin dynamics in cell motility. J. Mol. Biol. 1997; 269(4):459-67. [PMID: 9217250]
  6. Dominguez R. Actin filament nucleation and elongation factors–structure-function relationships. Crit. Rev. Biochem. Mol. Biol.; 44(6):351-66. [PMID: 19874150]
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Subpages (2): Actin binding proteins influence actin dynamics. A. Types of actin filament crosslinking proteins.
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