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 cleaves single-stranded DNA.
- 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 requires a free 5’ OH group for reacting.
- For phage ExN see Sand box 211.
Mg coordination site in E. coli exonuclease I (PDB code 1fxx).[2] Water molecules shown as red spheres.
3D Structures of exonuclease
Exonuclease 3D structures
- ↑ 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:https://dx.doi.org/10.1385/1-59259-750-5:193
- ↑ 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