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.

Domains D2 is exclusively composed of alpha-helices that form a helical bundle similar to the thumb domain of A-family DNA polymerases but due to its position in Cmr2 it cannot interact with the primer-template. Current studies suggest that the functional implication of structural resemblance between Cmr2 D2 and thumb domains is unclear.

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