This is a divergent version of the Receiver (Rec) domain linked to different NAD+/ADPr-processing enzymes. Unlike conventional Rec domains, cREC is never found in two-component Histidine Kinase signalling systems. Instead, it is found in association with NAD+-processing systems that generate or recognise cyclic nucleotides. Known Rec domains process phosphoester linkages by means of catalytic aspartate residues that are also conserved in cREC. Accordingly, it is predicted that these are cADPr or 2_-3_ cyclic nucleotide-processing enzymes.

1: Jumbo Phages: A Comparative Genomic Overview of Core Functions and Adaptions for Biological Conflicts. M Iyer L, Anantharaman V, Krishnan A, Burroughs AM, Aravind L; Viruses. 2021; [Epub ahead of print] PMID:33466489