Figure 4.

The same R1 trans subunit provides DDE residues in trans for sequential cleavage and strand transfer of one Mu DNA end. (A) Reactions were performed as described in Materials and Methods and Fig. 1 except that the nonbio substrate was replaced with an unjoinable substrate (see text). Released complexes were incubated with target DNA to permit strand transfer. Complexes that catalyzed strand transfer were isolated by separating these complexes from inactive complexes on a native agarose gel. (B) SDS-PAGE of gel-purified STC. Numbers above and below each lane are as described in Fig. 2.