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.
in E. coli exonuclease I (PDB code 1fxx).[2] Water molecules shown as red spheres.
