AC MF_00953; DC Protein; auto TR HAMAP; MF_00953; -; 1; level=0 XX Names: Topoisom_3_prok XX ID TOP3 DE RecName: Full=DNA topoisomerase 3; DE EC=5.6.2.1; DE AltName: Full=DNA topoisomerase III; GN Name=topB; XX CC -!- FUNCTION: Releases the supercoiling and torsional tension of DNA, which CC is introduced during the DNA replication and transcription, by CC transiently cleaving and rejoining one strand of the DNA duplex. CC Introduces a single-strand break via transesterification at a target CC site in duplex DNA. The scissile phosphodiester is attacked by the CC catalytic tyrosine of the enzyme, resulting in the formation of a DNA- CC (5'-phosphotyrosyl)-enzyme intermediate and the expulsion of a 3'-OH CC DNA strand. The free DNA strand then undergoes passage around the CC unbroken strand, thus removing DNA supercoils. Finally, in the CC religation step, the DNA 3'-OH attacks the covalent intermediate to CC expel the active-site tyrosine and restore the DNA phosphodiester CC backbone. CC -!- CATALYTIC ACTIVITY: CC Reaction=ATP-independent breakage of single-stranded DNA, followed by CC passage and rejoining.; EC=5.6.2.1; case CC -!- COFACTOR: CC Name=Mg(2+); Xref=ChEBI:CHEBI:18420; CC Note=Binds two Mg(2+) per subunit.; else case CC -!- COFACTOR: CC Name=Mg(2+); Xref=ChEBI:CHEBI:18420; end case CC -!- SIMILARITY: Belongs to the type IA topoisomerase family. XX DR PROSITE; PS00396; TOPO_IA_1; 1; trigger=no DR PROSITE; PS52039; TOPO_IA_2; 1; trigger=yes DR PROSITE; PS50880; TOPRIM; 1; trigger=yes DR Pfam; PF01131; Topoisom_bac; 1; trigger=no DR Pfam; PF01751; Toprim; 1; trigger=no DR PRINTS; PR00417; PRTPISMRASEI; 1; trigger=no DR NCBIfam; TIGR01056; topB; 1; trigger=no XX KW DNA-binding KW Isomerase case or KW Magnesium KW Metal-binding end case KW Topoisomerase XX GO GO:0003917; F:DNA topoisomerase type I (single strand cut, ATP-independent) activity case or GO GO:0000287; F:magnesium ion binding end case GO GO:0006265; P:DNA topological change XX FT From: TOP3_ECOLI (P14294) FT REGION 194..199 FT /note="Interaction with DNA" FT Optional; Condition: [SN]-x-G-R-V-Q FT ACT_SITE 328 FT /note="O-(5'-phospho-DNA)-tyrosine intermediate" FT Condition: Y case FT BINDING 7 FT /ligand="Mg(2+)" FT /ligand_id="ChEBI:CHEBI:18420" FT /ligand_label="1" FT /ligand_note="catalytic" FT Group: 1; Condition: E FT BINDING 103 FT /ligand="Mg(2+)" FT /ligand_id="ChEBI:CHEBI:18420" FT /ligand_label="1" FT /ligand_note="catalytic" FT Group: 1; Condition: D FT BINDING 103 FT /ligand="Mg(2+)" FT /ligand_id="ChEBI:CHEBI:18420" FT /ligand_label="2" FT Group: 1; Condition: D FT BINDING 105 FT /ligand="Mg(2+)" FT /ligand_id="ChEBI:CHEBI:18420" FT /ligand_label="2" FT Group: 1; Condition: D else FT BINDING 7 FT /ligand="Mg(2+)" FT /ligand_id="ChEBI:CHEBI:18420" FT /ligand_note="catalytic" FT Group: 2; Condition: E FT BINDING 103 FT /ligand="Mg(2+)" FT /ligand_id="ChEBI:CHEBI:18420" FT /ligand_note="catalytic" FT Group: 2; Condition: D end case FT SITE 61 FT /note="Interaction with DNA" FT Optional; Condition: W FT SITE 170 FT /note="Interaction with DNA" FT Optional; Condition: W FT SITE 178 FT /note="Interaction with DNA" FT Optional; Condition: R FT SITE 185 FT /note="Interaction with DNA" FT Optional; Condition: R FT SITE 330 FT /note="Interaction with DNA" FT Optional; Condition: R XX Size: 610-765; Related: None; Template: P14294; Scope: Bacteria Fusion: Nter: None Cter: None Duplicate: None Plasmid: None Comments: None XX # Revision 1.14 2023/10/06 //