Predicted ligand-binding domain of the PPC-like beta-sandwich fold. Observed in conserved gene neighbourhoods with diverse nucleotide-activated effector and related conflict systems, potentially recognises invasive molecules and initiates system responses or directly triggers directly-associated effector domains [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