This family represents an inactive member of the Receiver superfamily of the Rossmonnoid fold, predicted to function as a sensor domain in certain nucleotide-activated effector conflict systems. It is thought to bind nucleotides synthesized by both the SMODS domain and the CRISPR polymerase (Cpol) domain of the Cas10-like proteins, depending on genome context. N-terminal transmembrane segments are observed, suggesting that nucleotide binding initiates a membrane-perforating and cell-suicide response in conflict [1].

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