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 D4 domain adopts a six-helix bundle, which is homologous with structures of diverse functions. The most relevant structural homologue to D4 is Cmr5, another Cmr complex subunit, which suggests it may perform a similar function or they may interact with each other in the Cmr complex.

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