ID   TOP1_KLEAE              Reviewed;          18 AA.
AC   P46155;
DT   01-NOV-1995, integrated into UniProtKB/Swiss-Prot.
DT   01-NOV-1995, sequence version 1.
DT   25-MAY-2022, entry version 68.
DE   RecName: Full=DNA topoisomerase 1;
DE            EC=5.6.2.1 {ECO:0000255|PROSITE-ProRule:PRU10131};
DE   AltName: Full=DNA topoisomerase I;
DE   AltName: Full=Omega-protein;
DE   AltName: Full=Relaxing enzyme;
DE   AltName: Full=Swivelase;
DE   AltName: Full=Untwisting enzyme;
DE   Flags: Fragment;
GN   Name=topA;
OS   Klebsiella aerogenes (Enterobacter aerogenes).
OC   Bacteria; Proteobacteria; Gammaproteobacteria; Enterobacterales;
OC   Enterobacteriaceae; Klebsiella/Raoultella group; Klebsiella.
OX   NCBI_TaxID=548;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RC   STRAIN=NCTC 418 / ATCC 15380;
RX   PubMed=8166630; DOI=10.1042/bj2990129;
RA   Lynch A.S., Tyrrell R., Smerdon S.J., Briggs G.S., Wilkinson A.J.;
RT   "Characterization of the CysB protein of Klebsiella aerogenes: direct
RT   evidence that N-acetylserine rather than O-acetylserine serves as the
RT   inducer of the cysteine regulon.";
RL   Biochem. J. 299:129-136(1994).
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 (By similarity). {ECO:0000250}.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=ATP-independent breakage of single-stranded DNA, followed by
CC         passage and rejoining.; EC=5.6.2.1; Evidence={ECO:0000255|PROSITE-
CC         ProRule:PRU10131};
CC   -!- SUBUNIT: Monomer. {ECO:0000250}.
CC   -!- SIMILARITY: Belongs to the type IA topoisomerase family. {ECO:0000305}.
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DR   EMBL; X78729; -; NOT_ANNOTATED_CDS; Genomic_DNA.
DR   AlphaFoldDB; P46155; -.
DR   STRING; 548.EAG7_01158; -.
DR   GO; GO:0003677; F:DNA binding; IEA:UniProtKB-KW.
DR   GO; GO:0003917; F:DNA topoisomerase type I (single strand cut, ATP-independent) activity; IEA:UniProtKB-EC.
DR   GO; GO:0006265; P:DNA topological change; IEA:InterPro.
DR   InterPro; IPR013263; TopoI_Znr_bac.
DR   Pfam; PF08272; Topo_Zn_Ribbon; 1.
PE   3: Inferred from homology;
KW   DNA-binding; Isomerase; Topoisomerase.
FT   CHAIN           <1..18
FT                   /note="DNA topoisomerase 1"
FT                   /id="PRO_0000145152"
FT   NON_TER         1
SQ   SEQUENCE   18 AA;  2043 MW;  8C1C81238FF0EFA4 CRC64;
     ATGWSAFFID GKWTEAKK