F-actin-capping proteins bind in a Ca(2+)-independent manner to the fast growing ends of actin filaments (barbed end) thereby blocking the exchange of subunits at these ends. Unlike other capping proteins (such as gelsolin and severin), these proteins do not sever actin filaments. Competes with formin cdc12 for attachment to the actin filaments barbed ends. Slowly replaces cdc12 on the barbed ends in preparation for filament disassembly during contractile ring constriction. Heterodimer of an alpha and a beta subunit. Septum. Localizes to cell tips during interphase. Belongs to the F-actin-capping protein alpha subunit family.