"Modifies the topological state of DNA by introducing positive supercoils in an ATP-dependent process, increasing the linking number in steps of +1. Binds to single-stranded DNA, transiently cleaves and then rejoins the ends, introducing a positive supercoil in the process. The scissile phosphodiester is attacked by the catalytic tyrosine of the enzyme, resulting in the formation of a DNA-(5'-phosphotyrosyl)-enzyme intermediate. Probably involved in rewinding DNA strands in regions of the chromosome that have opened up to allow replication, transcription, DNA repair and/or for DNA protection."xsd:string