Reverse gyrase

UniProtKB accession:  O29238

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UniProtKB description:  Modifies the topological state of DNA by introducing positive supercoils in an ATP-dependent process, increasing the linking number in steps of +1 (PubMed:12048189, PubMed:12755601, PubMed:16407212). Very efficient supercoiling occurs on relaxed DNA with a single-stranded bubble; the minimal bubble is 20 nucleotides (nt) and up to 10 positive supercoils can be introduced into a 3.1 kb plasmid with a 50 nt bubble (PubMed:16407212). Positively supercoils DNA with all (d)NTPS, although it requires about 10-fold more of non-(d)ATP (PubMed:12048189). In the absence of ATP (or at low levels of enzyme), or in the presence of ADP, relaxes negative supercoils (PubMed:12048189, PubMed:12755601, PubMed:16407212). Only relaxes positive supercoils when the substrate contains a bubble (PubMed:16407212). Also promotes strand annealing of complementary ssDNA circles (PubMed:16407212). 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 (PubMed:16407212) (Probable).