CRISPR type V
SEE CRISPR-Cas The prototype type V effector Cpf1 (subtype V-A) contains only one nuclease domain (RuvC-like) that is identifiable by sequence analysis. However, analysis of the recently solved structure of Cpf1 complexed with the crRNA and target DNA has revealed a second nuclease domain, the fold of which is unrelated to HNH or any other known nucleases. In analogy to the HNH domain in Cas9, the novel nuclease domain (labeled Nuc) in Cpf1 is inserted into the RuvC domain, and it is responsible for cleavage of the target strand.[1][2] Screening of microbial genomes and metagenomes for undiscovered class 2 systems has resulted in the identification of three novel CRISPR-Cas variants. These include subtypes V-B and V-C, which resemble Cpf1 in that their predicted effector proteins contain a single, RuvC-like nuclease domain. Cleavage of target DNA by the type V-B effector, denoted C2c1, has been experimentally demonstrated. Type VI is unique in that its effector protein contains two conserved HEPN domains that possess ribonuclease (RNase) activity.[1][3]
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