Exonuclease

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Exonucleases (ExN) cleave nucleotides at the end of a polynucleotide chain[1]. In E. coli there are ExN I to VIII. ExN were found in human and yeast as well.


  • ExN-I is a 5'-3' ExN cleaves double-stranded DNA[2].
  • ExN-II is associated with DNA polymerase.
  • ExN-III cleaves double-stranded DNA.
  • ExN-IV cleavage results in nucleoside monophosphate.
  • ExN-V cleaves linear double-stranded DNA.
  • ExN-VIII degrades linear duplex DNA[3] and requires a free 5’ OH group for reacting.
  • ExN-X can degrade both single-stranded DNA and duplex DNA with 3'-5' polarity[4]
  • Trex ExN degrades single-stranded DNA generated from processing of aberrant replication intermediates[5]

Mg coordination site in E. coli exonuclease I (PDB code 1fxx).[6] Water molecules shown as red spheres.

3D Structures of exonuclease

Exonuclease 3D structures


E. coli exonuclease I complex with phosphate, glycerol and Mg+2 ion (PDB code 1fxx)

Drag the structure with the mouse to rotate

References

  1. ↑ Mukherjee D, Fritz DT, Kilpatrick WJ, Gao M, Wilusz J. Analysis of RNA exonucleolytic activities in cellular extracts. Methods Mol Biol. 2004;257:193-212. PMID:14770007 doi:http://dx.doi.org/10.1385/1-59259-750-5:193
  2. ↑ Keijzers G, Liu D, Rasmussen LJ. Exonuclease 1 and its versatile roles in DNA repair. Crit Rev Biochem Mol Biol. 2016 Nov/Dec;51(6):440-451. PMID:27494243 doi:10.1080/10409238.2016.1215407
  3. ↑ Joseph JW, Kolodner R. Exonuclease VIII of Escherichia coli. II. Mechanism of action. J Biol Chem. 1983 Sep 10;258(17):10418-24 PMID:6309804
  4. ↑ Viswanathan M, Lovett ST. Exonuclease X of Escherichia coli. A novel 3'-5' DNase and Dnaq superfamily member involved in DNA repair. J Biol Chem. 1999 Oct 15;274(42):30094-100. PMID:10514496 doi:10.1074/jbc.274.42.30094
  5. ↑ Yang YG, Lindahl T, Barnes DE. Trex1 exonuclease degrades ssDNA to prevent chronic checkpoint activation and autoimmune disease. Cell. 2007 Nov 30;131(5):873-86. doi: 10.1016/j.cell.2007.10.017. PMID:18045533 doi:http://dx.doi.org/10.1016/j.cell.2007.10.017
  6. ↑ Breyer WA, Matthews BW. Structure of Escherichia coli exonuclease I suggests how processivity is achieved. Nat Struct Biol. 2000 Dec;7(12):1125-8. PMID:11101894 doi:10.1038/81978

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