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Alternative titles; symbols
ARP3
TEXT
The Arp2/3 protein complex has been implicated in the control of actin polymerization in cells. The human complex consists of 7 subunits: the actin-related proteins ARP2 (ACTR2; 604221) and ARP3 (ACTR3), ARC41 (ARPC1B; 604223), ARC34 (ARPC2; 604224), ARC21 (ARPC3; 604225), ARC20 (ARPC4; 604226), and ARC16 (ARPC5; 604227). See ACTR2 for additional information about the Arp2/3 complex. 
CLONING
By searching an EST database with peptide sequences from the 7 subunits of the human ARP2/3 complex, Welch et al. (1997) identified full-length human cDNAs encoding each subunit. The ARP3 cDNA encodes a deduced 418-amino acid protein that is identical to bovine Arp3, 59% identical to S. pombe Arp3, and 58% identical to S. cerevisiae Arp3. ARP3 localizes to the lamellipodia of stationary and locomoting fibroblasts. It also localizes to the actin tails assembled by moving intracellular Listeria monocytogenes bacteria and to actin clouds surrounding stationary L. monocytogenes (Welch et al., 1997). ARP3 was not detected in cellular bundles of actin filaments.
Machesky et al. (1997) purified the ARP2/3 complex from human neutrophils and sequenced peptides from each of the subunits. Western blot analysis detected ARP3 and ARC34 in all human tissues tested.
BIOCHEMICAL FEATURES
Volkmann et al. (2001) performed electron cryomicroscopy and 3-dimensional reconstruction of Acanthamoeba castellanii and S. cerevisiae Arp2/3 complexes bound to the WASP (301000) carboxy-terminal domain. Asymmetric, oblate ellipsoids were revealed. Image analysis of actin branches indicated that the complex binds the side of the mother filament, and ARP2 and ARP3 are the first 2 subunits of the daughter filament. Comparison to the actin-free WASP-activated complexes suggests that branch initiation involves large-scale structural rearrangements within ARP2/3.
Robinson et al. (2001) determined the crystal structure of bovine ARP2/3 complex at 2.0-angstrom resolution. ARP2 and ARP3 are folded like actin, with distinctive surface features. Subunits ARPC2 and ARPC4 in the core of the complex associate through long carboxy-terminal alpha helices and have similarly folded amino-terminal alpha/beta domains. ARPC1 is a 7-blade beta propeller with an insertion that may associate with the side of an actin filament. ARPC3 and ARPC5 are globular alpha-helical subunits. Robinson et al. (2001) predicted that WASP/SCAR proteins activate ARP2/3 complex by bringing ARP2 into proximity with ARP3 for nucleation of a branch on the side of a preexisting actin filament.
REFERENCES
- 1. Machesky, L. M.; Reeves, E.; Wientjes, F.; Mattheyse, F. J.; Grogan, A.; Totty, N. F.; Burlingame, A. L.; Hsuan, J. J.; Segal, A. W. :
- Mammalian actin-related protein 2/3 complex localizes to regions of lamellipodial protrusion and is composed of evolutionarily conserved proteins. Biochem. J. 328: 105-112, 1997.
PubMed ID : 9359840
- 2. Robinson, R. C.; Turbedsky, K.; Kaiser, D. A.; Marchand, J.-B.; Higgs, H. N.; Choe, S.; Pollard, T. D. :
- Crystal structure of Arp2/3 complex. Science 294: 1679-1684, 2001.
PubMed ID : 11721045
- 3. Volkmann, N.; Amann, K. J.; Stoilova-McPhie, S.; Egile, C.; Winter, D. C.; Hazelwood, L.; Heuser, J. E.; Li, R.; Pollard, T. D.; Hanein, D. :
- Structure of Arp2/3 complex in its activated state and in actin filament branch junctions. Science 293: 2456-2459, 2001.
PubMed ID : 11533442
- 4. Welch, M. D.; DePace, A. H.; Verma, S.; Iwamatsu, A.; Mitchison, T. J. :
- 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: 375-384, 1997.
PubMed ID : 9230079
- 5. Welch, M. D.; Iwamatsu, A.; Mitchison, T. J. :
- Actin polymerization is induced by Arp2/3 protein complex at the surface of Listeria monocytogenes. Nature 385: 265-269, 1997.
PubMed ID : 9000076
CONTRIBUTORS
Ada Hamosh - updated : 1/10/2002
Ada Hamosh - updated : 10/11/2001
Patti M. Sherman - updated : 10/29/1999
CREATION DATE
Patti M. Sherman : 10/8/1999
EDIT HISTORY
alopez : 1/10/2002
alopez : 1/10/2002
alopez : 10/11/2001
mgross : 11/1/1999
psherman : 10/29/1999
mgross : 10/15/1999
psherman : 10/12/1999
psherman : 10/12/1999
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