Enables small GTPase binding activity. Contributes to superoxide-generating NAD(P)H oxidase activity. Acts upstream of or within superoxide anion generation. Located in acrosomal vesicle. Is expressed in several structures, including hemolymphoid system; limb; and liver. Human ortholog(s) of this gene implicated in Alzheimer's disease; autosomal recessive chronic granulomatous disease cytochrome b-positive type II; and rheumatoid arthritis. Orthologous to human NCF2 (neutrophil cytosolic factor 2). [provided by Alliance of Genome Resources, Apr 2022]