Advances in CRISPR/Cas9

Figure 2

The overall structure of the Cas9 protein and the schematic diagram of the Cas9–sgRNA-target DNA complex in a type II CRISPR/Cas system. Cas9 protein comprises NUC and REC lobes. REC lobe contains a long alpha helix and two REC domains. NUC lobe consists of PI, RuvC, and HNH domains. RuvC and HNH domains have cleavage functions, which can recognize the PAM site and cut the target DNA under the guide of the crRNA: tracrRNA complex [25, 28].