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. Isoform 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. Plays a role in the regulation of cell morphology and cytoskeletal organization (By similarity). 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. Isoform 2 also is a component of dynactin complex from brain, which contains the actin-related protein ARP1. Interacts with ACTG1. Directly interacts with CRACD; this interaction decreases binding to actin (By similarity). In cardiac muscle, isoform 1 is located at Z-disks of sarcomeres while isoform 2 is enriched at intercalated disks. Isoform 3 is located to sperm head cytoskeletal structure tightly associated to the nucleus (By similarity). Isoform 3 colocalizes with the alpha subunit in testicular sperm and to the acrosome in elongating and condensing spermatids. Isoform 3 is testis-specific and is present in round spermatids, but not in pachytene spermatocytes or Sertoli cells. Isoform 3 is first detected in testis 22 days after birth, coinciding with the first wave of round spermatid development. It is also detected on 30 and 60 days after birth. Belongs to the F-actin-capping protein beta subunit family.