Relaxation reaction of protein TrwCR with different plasmid DNAs containing mutant oriTs. A, 20 μl of plasmids (10 nm). Lane 1, pSU18; lane 2, pSU4910; lane 3, pSU1671 (mut28–29; lane 4, pSU1672 (mut26–27); lane 5, pSU1673 (mut23–25); lane 6, pSU1674 (mut20–22); lane 7, pSU1675 (mut18–19); lane 8, pSU1676 (mut13–17); lane 9, pSU1677 (mut8–11); lane 10, pSU1678 (mutIR); lane 11, pSU1679 (mut4–7). B, relaxation products of the same plasmids as in A. TrwCR (300 nm) was incubated with DNA (10 nm) in the presence of 10 mm Tris, pH 7.6, 50 mm NaCl, 0.02 mm EDTA, and 5 mm MgCl2 for 30 min at 37 °C. Then the reaction mixture was digested with proteinase K. C, DNA-protein covalent complex precipitation in the presence of KCl. The lanes correspond to the plasmids indicated in A. sc, supercoiled; oc, open circle.