topA [2017-12-18 10:19:58]

DNA topoisomerase I

Locus: BSU16120

Isoelectric point: 9.02

Molecular weight: 78.89 kDa

Protein length: 691 aa

Gene length: 2073 bp

Function: relaxation of negatively supercoiled DNA

Product: DNA topoisomerase I

Essential: yes

E.C.: 5.99.1.2

Synonyms: topI

Genomic Context

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Categories containing this gene/protein

• Information processing → Genetics → DNA condensation/ segregation
• Groups of genes → Efp-dependent proteins
• Groups of genes → Quasi-essential genes

Gene

Coordinates: 1,683,661 → 1,685,736

Phenotypes of a mutant

• essential PubMed, non-essential according to PubMed, but only one resistance cassette was possible

The protein

Catalyzed reaction/ biological activity

• relaxation of negatively supercoiled DNA

Protein family

• prokaryotic type I/III topoisomerase family (according to Swiss-Prot)

Paralogous protein(s)

• TopB

Domains

• N-terminal TOPRIM domain (aa 3-114) PubMed

Structure

• 2GAI (from Thermotoga maritima , 42% identity) PubMed

Additional information

• TopA may interact with RNA polymerase PubMed
• mutations affecting Val-44 (V44D) and Ser-478 (S478P) result in TopA hyperactivity PubMed

Expression and Regulation

Operons

• Genes: sucC-sucD-dprA-topA
  Description: PubMed

  Regulatory mechanism

  • CcpA: repression, PubMed, in CcpA regulon

  Regulation

  • repressed by glucose (2.4-fold) (CcpA) PubMed
  • expression is heterogeneous PubMed

• Genes: topA
  Description: PubMed

  Additional information

  • translation is likely to require Efp due to the presence of several consecutive proline residues PubMed

Biological materials

Mutant

• BKK16120 (ΔtopA::kan trpC2) available at BGSC, PubMed, upstream reverse: _UP1_CATTTTCATCCCCCTCAAGA, downstream forward: _UP4_TAGCGGTGAGCAGGGTCTTG

Expression vector

• pGP2060: IPTG inducible expression, purification in E. coli with N-terminal Strep-tag, in pGP172, available in Jörg Stülke's lab

References

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