incubation of rat liver single-strand dna binding protein s25 with covalently closed relaxed sv40 dna in the presence of rat liver topoisomerase i induced a decrease in the linking number lk of dna , so that it appeared negatively supertwisted after removal of the protein . delta lk was found to be a linear function of protein to dna ratio and reached a plateau corresponding to about 15 superhelical turns .
C0000702
a
C0012854
dna