Actin-binding adapter protein. Binds to F-actin but is not involved in actin polymerization, capping or bundling. Does not bind G-actin. Controls pseudopodium number and motility in early stages of chemotactic aggregation. The SH3 domain mediates the control of pseudopodium number. Belongs to the ABP1 family. The gene for this protein is duplicated in strains AX3 and AX4. These strains contain a duplication of a segment of 750 kb of chromosome 2 compared to the corresponding sequence in strain AX2.