Part of an actin-like archaeal cytoskeleton (PubMed:21414041). Prevents polymerization of crenactin filaments by binding its C-terminus into crenactin's hydrophobic groove. May act by competing with the D-loop of the following crenactin subunit for the hydrophobic groove (PubMed:27852434). Interacts with crenactin. Localizes between segregated nucleoids. The C-terminal helix is essential for activity. Belongs to a conserved five-gene operon within Thermoproteales denoted Arcade (actin-related cytoskeleton in Archaea involved in shape determination).