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Actin Related Proteins (ARPs)

Rob Insall's Arp2/3 website 

The actin-related proteins (Arps) are a group of proteins with sequence similarity to actin. Although  they  are all recognisable homologous to actin, they are a very diverse, each Arp group performing very different functions in cells. For example one actin-related protein, ArpX, is known to be present in the nucleus where it is thought to work together with  heterochromatin protein 1 (HP1), to perform heterochromatin-mediated gene silencing and alterations in chromatin structure (Frankel et al, 1997), and another (Arp1) is part of the dynactin complex that controls microtubule motility.  There are some 10 members of the Arp family in yeast .  Arps will be discussed in their numerical order.

ARP1 (centractin).  9 Arp1 molecules polymerise to form a short filament, probably resembling an actin filament.  This is capped at the barbed end by CapZ, the dimeric (genuine) actin binding protein, and possibly by p62 at the pointed end (Garces et al, 1999).  The Arp1 filament is bound by p150 glued (Figure 1), and by spectrin (Holleran et al, 1996).  Binding of the complex to vesicle specific spectrins may be a mechanism for targeting motility of particular vesicle populations (see Golgi Cytoskeleton).

ARP2/3.  A heterodimeric complex that together with some seven other proteins caps the pointed end of actin filaments.  This complex was discovered by Machesky and colleagues (Machesky & Pollard, 1992 ).  Recent evidence (Jay et al, 2000) indicates that the expression of these Arps may be complicates by alternative splicing.

ARP4.  There is slight confusion over Arp4 since Drosophila "Arp4"an intra-nuclear Arp is not very similar to Arp4 from Saccaromcyes cerevisae a protein which  itself is known as Act3p and Arp6!







ARP11.  This Arp is another pointed end capper (like the Arp2/3 complex), but Arp11 caps the minifilament composed of Arp1 in the dynactin complex (Eckley et al, 1999).


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Frankel, S., E. A. Sigel, et al. (1997). "An actin-related protein in Drosophila colocalizes with heterochromatin protein 1 in pericentric heterochromatin." J.Cell Sci. 110, 1999-2012.

Garces, J. A., I. B. Clark, et al. (1999). "Interaction of the p62 subunit of dynactin with Arp1 and the cortical actin cytoskeleton." Curr.Biol. 9, 1497-1500.

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Machesky, L. M. & R. H. Insall (1998). "Scar1 and the related Wiskott-Aldrich syndrome protein WASP, regulate the actin cytoskeleton through the ARP2/3 complex." Curr.Biol. 8, 1347-1356.

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Mullins, R. D., J. A. Heuser, et al. (1998). "The interaction of ARP2/3 complex with actin: nucleation, high affinity pointed end capping, formation of branching networks of filaments." Proc.Nat.Acad.Sci.USA 95, 6181-6186.

Mullins, R. D., J. F. Kelleher, et al. (1998). "Arp2/3 complex from Acanthamoeba binds profilin and cross-links actin filaments." Mol.Cell Biol. 9, 841-852.

Mullins, R. D. & T. D. Pollard (1999). "Rho-family GTPases require the Arp2/3 complex to stimulate actin polymerization in Acanthamoeba extracts." Curr. Biol. 9, 405-415.

Mullins, R. D. & T. D. Pollard (1999). "Structure and function of the Arp2/3 complex." Curr.Op.Struct.Biol. 9, 244-249.

Mullins, R. D., W. F. Stafford, et al. (1997). "Structure, subunit topology, and actin-binding activity of the Arp2/3 complex from Acanthamoeba." J.Cell Biol. 136, 331-343.

Pantaloni, D., R. Boujemaa, et al. (2000). "The Arp2/3 complex branches filament barbed ends: functional antagonism with capping proteins." Nature Cell Biol. 2, 385-391.

Peterson, C. L., Y. Zhao, et al. (1998). "Subunits of the yeast SWI/SNF complex are members of the actin-related protein (ARP) family." J.Biol.Chem. 273(37), 23641-23644.

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Rozelle, A. L., L. M. Machesky, et al. (2000). "Phosphatidylinositol 4,5-bisphosphate induces actin-based movement of raft-enriched vesicles through WASP-Arp2/3." Current Biology 10, 311-320.

Schaerer-Brodbeck, C. and H. Riezman (2000). "Functional interactions between the p35 subunit of the Arp2/3 complex and calmodulin in yeast." Mol.Biol.Cell 11, 1113-1127.

Schroer, T. A. (1994). "New insights into the interaction of cytoplamsic dynein with the actin-related protein, Arp1." J.Cell Biol. 127(1), 1-4.

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Svitkina, T. M. and G. G. Borisy (1999). "Arp2/3 complex and actin depolymerizing factor/cofilin in dendritic organization and treadmilling of actin filament array in lamellipodia." J.Cell Biol. 145, 1009-1026.

Welch, M. D. (1999). "The world according to ARP: regulation of actin nucleation by the Arp2/3 complex." Trends Cell Biol. 9, 423-427.

Welch, M. D., A. H. DePace, et al. (1997). "The human Arp2/3 complex is composed of evolutionarily conserved subunits and is localized to cellular regions of dynamic actin filament assembly." J.Cell Biol. 138(2), 375-384.

Welch, M. D., A. Iwamatsu, et al. (1997). "Actin polymerization is induced by Arp2/3 protein complex at the surface of Listeria monocytogenes." Nature 385, 265-269.

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Yarar, D., W. To, et al. (1999). "The Wiskott-Aldrich syndrome protein directs actin-based motility by stimulating actin nucleation with the Arp2/3 complex." Curr.Biol. 9, 555-558.

Zigmond, S. H. (1998). "Actin cytoskeleton: The Arp2/3 complex gets to the point." Current Biol. 8, 654-657.


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