Figure 3.

RecJ cleaves the terminal nucleotides on 5′ tails. DNA substrates with 5′ single-stranded tails of 5, 6, 7, 8 and 9 nt in length were subjected to conditions where RecJ binding only could be observed [(B), no Mg²⁺] and conditions where nuclease activity could be detected [(C), 10 mM MgCl₂] by loss of radioactive label at the 5′ end of the single-stranded tail. The 5 nM RecJ protein was combined with 5 nM substrate in binding reactions whereas 12.5 nM protein was combined with 5 nM substrate in cleavage reactions. Control reactions (A) contained no protein.