Reverse gyrase

UniProtKB accession:  O51934

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UniProtKB description:  Modifies the topological state of DNA by introducing positive supercoils in an ATP-dependent process (PubMed:9440516, PubMed:18614530, PubMed:21051354, PubMed:23209025). Increases the linking number in steps of +1 (PubMed:23209025) (Probable). Probably recognizes regions with a low GC content which melt and form a ssDNA bubble, allowing the enzyme to bind and cleave the DNA prior to strand passage; the bubble is probably cleaved by 2 reverse gyrase molecules, one on each strand (PubMed:32592697) (Probable). Positively supercoils DNA with all NTPS, although it strongly prefers ATP (PubMed:18614530). In the presence of non-hydrolyzable ATP analogs it partially relaxes negative supercoils (PubMed:18614530, PubMed:21051354, PubMed:32592697). Has an intrinsic ATPase activity that is stimulated by DNA; ssDNA is most effective (PubMed:18614530, PubMed:21051354, PubMed:32592697). 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 (PubMed:18614530, PubMed:32592697) (Probable). The helicase-like domain is a nucleotide-dependent switch that alternates between a physically closed ATP-bound state with a slight preference for dsDNA, and an open ADP-bound state with a high preference for ssDNA (PubMed:21350762). Whole enzyme has a very poor (k-unwind=0.001 sec(-1)) non-processive helicase activity in the 3'-5' direction that works on short substrates, while the isolated helicase domain has a slightly better helicase activity that works in both directions (PubMed:23123378). 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.