Figure 7.

H-NS constrains DNA supercoils in vitro. Form-I DNA (1 μg) was incubated with the indicated amounts of purified H-NS protein and then treated with topoisomerase I. After deproteinization, DNA samples were electrophoresed on 0.8% agarose gel to resolve the topoisomers. Lane 1, the positions of form I and form IV (relaxed) DNA and positively supercoiled [(+) SC DNA] are shown in the left-hand side. Lane: 2, DNA incubated with topoisomerase I in the absence of H-NS; 3–8, contained topoisomerase I and indicated amounts of H-NS.