The CRISPR–Cas (clustered regularly interspaced short palindromic repeats–CRISPR-associated proteins) systems are immunity systems that are present in many bacteria and archaea. Here, Koonin and colleagues present a new classification of these systems and introduce a new nomenclature of the genes in the CRISPR–casloci that better reflects the relationships between the proteins.
- Kira S. Makarova
- Daniel H. Haft
- Eugene V. Koonin
