Single Staphylococcus aureus SauUSI restriction enzyme motors fragment methylated DNA.

SauUSI restriction enzyme motors fragment methylated DNA through ATP-driven translocation and looping, ultimately generating DNA fragments with blunt or 1-nt 3' overhangs.

• Why it matters: Understanding how SauUSI recognizes and cleaves methylated DNA reveals mechanisms of bacterial defense against foreign genetic material, filling a gap in knowledge about type IV restriction enzymes.
• What they did: Using biophysical, single-molecule, and nanopore sequencing methods, the study examined 5-methylcytosine recognition, ATP-driven translocation, DNA looping, and cleavage patterns in S. aureus SauUSI enzymes.
• The result: Multiple cycles of binding, translocation, and cleavage by individual enzymes fragment methylated DNA, which may enhance bacterial immunity by neutralizing foreign methylated DNA.