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. The isoform beta-3 may play a role in spermatogenesis. Alternatively, may play a role in later maturation steps such as capacitation and fertilization which involve changes of membrane domains. May play a role in the regulation of cell morphology and cytoskeletal organization. Heterodimer of an alpha and a beta subunit. Interacts with ARHGAP17 and RCSD1/CAPZIP. Component of the WASH complex, composed of F-actin-capping protein subunit alpha (CAPZA1, CAPZA2 or CAPZA3), F-actin-capping protein subunit beta (CAPZB), WASHC1, WASHC2, WASHC3, WASHC4 and WASHC5. Interacts with ACTG1. Directly interacts with CRACD; this interaction decreases binding to actin (By similarity). Sperm head cytoskeletal structure tightly associated to the nucleus. The isoform beta-3 is predominantly expressed in the testis. It is only detected in total sperm, sperm heads and the calyx fraction, but not in sperm tails or any supernatant fraction. Weaker expression also found in brain. Belongs to the F-actin-capping protein beta subunit family.