Arp2/3 complex in Drosophila melanogaster

The Arp2/3 complex is a seven-subunit actin nucleator that binds the side of an existing actin filament and starts a new filament at a 70 degree angle, producing branched actin networks. Two actin-related proteins, Arp2 and Arp3, form the template for the daughter filament, while the five ARPC subunits (ARPC1-ARPC5) hold them in place and contact the mother filament. The complex is intrinsically inactive and is switched on by nucleation-promoting factors such as SCAR/WAVE and WASp. In Drosophila, Arp2/3-driven branched actin is needed for lamellipodia, ring canal growth, myoblast fusion and many other processes. Drosophila has two ARPC3 paralogs, Arpc3A and Arpc3B, so two forms of the complex are possible.

FlyBase defines two complexes, ARPC3A and ARPC3B variants, that differ only in the ARPC3 paralog; they are modelled as one complex with an EXACTLY_ONE choice at the ARPC3 position. Whether the two variants differ in activity or expression is not established here. Nucleation-promoting factors (SCAR/WAVE regulatory complex, WASp) are upstream regulators and are not parts (see dmel_wave_regulatory_complex). No molecular function is assigned. GO has no molecular function term for Arp2/3-mediated actin nucleation, which is captured as a process; the fly subunits carry only structural constituent of cytoskeleton (ISS) and actin filament binding (IBA). FlyBase groups realized by this module: ARPC-C (FBgg0001797). Subgroups folded into it: ARPC3A, ARPC3B. Participants were generated from the FlyBase gene-group membership and mapped to UniProtKB by projects/FLYBASE_GENE_GROUPS/generate_modules.py from module_specs/dmel_arp2_3_complex.yaml. None of the member genes has a gene review in this repository yet.