Actin monomer binding protein that accelerates the exchange of ADP for ATP. Regulates the pool of unpolymerized ATP-actin. Key intermediate between actin-depolymerizing factor (ADF)-mediated disassembly and the profilin-based nucleation and elongation machinery. Expressed in roots, cotyledons, leaves, stems, flowers, pollen and shoots. Not detected in siliques. The C-terminal domain (318-476) binds to actin. Stunted growth and reduced pollen germination and growth. Belongs to the CAP family.