A pentameric complex that includes orthologues of human PIR121, Nap1, Abi, SCAR, and HSPC300 and regulates actin polymerization and/or depolymerization through small GTPase mediated signal transduction. [ GOC:hla http://www.ncbi.nlm.nih.gov/pubmed/24630101 GOC:pg http://www.ncbi.nlm.nih.gov/pubmed/24036345 http://www.ncbi.nlm.nih.gov/pubmed/12181570 ]