A dual-function helicase–nuclease, typified by RecBCD in Escherichia coli, acts on free DNA ends during bacterial double-stranded break repair until it reaches a χ sequence at which it pauses before continuing with modified enzymatic properties; here several crystal structures of the related AddAB enzyme from Bacillus subtilis bound to χ-containing DNA are presented, offering insight into χ recognition and its effect on DNA translocation.
- Wojciech W. Krajewski
- Xin Fu
- Dale B. Wigley
