Cas12j is an RNA-guided nuclease that bacteriophages use for DNA cutting and genome editing . The structure of Cas12j (7M5O) contains a protein of 763 residues (residues 1-52 and 717-763 unmodeled) and a single-stranded crRNA molecule of 45 nucleotides. In addition, there is a Zn ion bound in the zinc finger part of the protein. The crRNA forms a hairpin loop with the first 23 nucleotides, and it continues as a single stranded spacer region that is used to recognize the DNA sequence to be cut.