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. May play a role in the morphogenesis of spermatid (By similarity). Heterodimer of an alpha and a beta subunit (By similarity). Component of the WASH complex, composed of F-actin-capping protein subunit alpha (CAPZA1, CAPZA2 or CAPZA3), F-actin-capping protein subunit beta (CAPZB), WASH (WASHC1, WASH2P, WASH3P, WASH4P, WASH5P or WASH6P), WASHC2 (WASHC2A or WASHC2C), WASHC3, WASHC4 and WASHC5. Expressed exclusively in testis and sperm. Highest expression is found in the neck region of ejaculated sperm with lower levels found in the tail and postacrosome region. Belongs to the F-actin-capping protein alpha subunit family.