Cmr2 is a subunit of CRISPR RNA-Cas protein complex and belongs to the greater Cas10 family of proteins. Its function is the recognition and cleavage of foreign RNA to protect prokaryotes from invading genetic elements. Cmr2 lacking the N-terminal HD (Histidine-Aspartate) hydrolase domain (Cmr2dHD) is fully functional in RNA cleavage as part of the Cmr complex.

The N-terminal domain D1 contains a ferredoxin-like fold (which contains a P-loop) and a cysteine cluster that is formed by two CXXC motifs. It is the largest of the four domains of Cmr2 and is composed of nine helices and three beta-strands. ADP binds near the P-loop region of the D1 domain. The D1 domain that constitutes one face of the active site pocket might fulfil the role of fingers domain (similarly to DNA polymerases) in binding the nucleotide.

DOI:10.1016/j.str.2012.01.018,DOI:10.1016/j.febslet.2012.02.036