DNA damaging agents such as the anti-tumour drugs bleomycin and neocarzinostatin or those that generate oxygen radicals produce a variety of lesions in DNA. Amongst these is base-loss which forms apurinic/apyrimidinic (AP) sites or strand breaks with atypical 3' termini. DNA repair at the AP sites is initiated by specific endonuclease cleavage of the phosphodiester backbone. Such endonucleases are also generally capable of removing blocking groups from the 3' terminus of DNA strand breaks.AP endonucleases can be classified into two families based on sequence similarity. This family contains members of AP endonuclease family1. Except for Rrp1 and arp, these enzymes are proteins of about 300 amino-acid residues. Rrp1 and arp both contain additional and unrelated sequences in their N-terminal section (about 400 residues for Rrp1 and 270 for arp). This entry represents a motif containing a glutamate residue which has been shown in the Escherichia coli enzyme to bind a divalent metal ion such as magnesium or manganese [].
DNA damaging agents such as the anti-tumour drugs bleomycin and neocarzinostatin or those that generate oxygen radicals produce a variety of lesions in DNA. Amongst these is base-loss which forms apurinic/apyrimidinic (AP) sites or strand breaks with atypical 3' termini. DNA repair at the AP sites is initiated by specific endonuclease cleavage of the phosphodiester backbone. Such endonucleases are also generally capable of removing blocking groups from the 3' terminus of DNA strand breaks.AP endonucleases can be classified into two families based on sequencesimilarity. This family contains members of AP endonuclease family 1. Except for Rrp1 and arp, these enzymes are proteins of about 300 amino-acid residues. Rrp1 and arp both contain additional and unrelated sequences in their N-terminal section (about 400 residues for Rrp1 and 270 for arp). The proteins contain glutamate which has been shown []in the Escherichia coli enzyme to bind a divalent metal ion such as magnesium or manganese.
