One of two constant domains forming the CATRA module which is in turn C-terminally fused to a diverse range of conflict effector domains. This gene, along with a gene encoding the CATASP domain and a gene encoding a TPR repeat region fused to a CASPASE domain, forms the three gene island making up the CATRA conflict systems. This all alpha-helical domain is predicted to be involved in recognition of invasive molecules or in the transmitting of a signal through conformational change, enabling CASPASE-mediated proteolysis to free the fused effector domains.

1: Identification of Uncharacterized Components of Prokaryotic Immune Systems and Their Diverse Eukaryotic Reformulations. Burroughs AM, Aravind L; J Bacteriol. 2020; [Epub ahead of print] PMID:32868406