3.1.11.2	evolution	in general, DNA recombination in Escherichia coli accompanies the conversion of double-stranded DNA to single-stranded DNA by exonuclease. It is reported that Escherichia coli has at least seven exonucleases that prefer double-stranded DNA for their substrates: XthA, RecE, ExoX, RecBCD, SbcCD, Nfo, and TatD. In addition, YgdG is an exonuclease with yet undetermined substrate preference. It seems likely that Escherichia coli K-12 originally acquired iVEC activity, and the iVEC activity was involved in an unknown physiological function in Escherichia coli	750978	
3.1.11.2	malfunction	deletion of the DNA polymerase domain of PolA does not completely abrogate iVEC activity	750978	
3.1.11.2	metabolism	involvement of DNA polymerases in in vivo cloning of Escherichia coli (iVEC) activity, analysis of iVEC activities of various strains, which are deletion mutants of nonessential polymerases in the Keio collection, overview. XthA plays a critical role in the iVEC activity	750978	
3.1.11.2	additional information	enzyme residues E57 and D251 are critical for catalysis, molecular modelling and mutational analysis. Determinants of abasic-site recognition, overview. Homology modeling of MtbXthA using the structure of the Neisseria meningitidis protein (PDB ID 2JC4) as a template	-, 749954	
3.1.11.2	additional information	the PIP motif mediates critical interactions between AP endonuclease and proliferating cell nuclear antigen (PCNA), both in vitro and in vivo. The PIP motif in PCNA-interacting proteins is a defined consensus sequence (QxxLxxFF), while the consensus sequence corresponding to the beta-clamp interacting motif in prokaryotes is relatively less conserved. Structure comparison of homodimeric mycobacterial beta-clamp and homotrimeric human PCNA, overview	-, 751601	
3.1.11.2	physiological function	Escherichia coli has an ability to assemble DNA fragments with homologous overlapping sequences of 15 to 40 bp at each end. In vivo cloning of Escherichia coli (iVEC) is independent of both RecA and RecET recombinases but is dependent on XthA, a 3' to 5' exonuclease. XthA resects the 3' ends of linear DNA fragments that are introduced into Escherichia coli cells, resulting in exposure of the single-stranded 5' overhangs. Then, the complementary single-stranded DNA ends hybridize each other, and gaps are filled by DNA polymerase I, molecular iVEC mechanism, overview. XthA helps to repair minor DNA damage, instead of the RecBCD exonuclease. RecBCD produces a 3' overhang and loads RecA onto the single-stranded DNA, causing an SOS response accompanied by cell division arrest. To help avoid such a serious outcome, it is conceivable that XthA functions in a repair pathway of DNA damage	750978	
3.1.11.2	physiological function	exonuclease III (Exo III) is a sequence-independent 3'-5' exonuclease	752287	
3.1.11.2	physiological function	exonuclease III (Exo III) plays crucial roles in maintaining the genome stability	749571	
3.1.11.2	physiological function	key enzyme involved in the repair of abasic sites and DNA strand breaks	-, 750388	
3.1.11.2	physiological function	MtbXthA is a versatile enzyme withAP endonuclease, 3'-5' exonuclease and 3' phosphodiesterase activities. the sliding DNA beta-clamp forms in vivo and in vitro complexes with XthA in Mycobacterium tuberculosis. A novel 239QLRFPKK245 motif in the DNA-binding domain of XthA is found to be important for the interactions. Likewise, the peptide binding-groove (PBG) and the C-terminal of beta-clamp located on different domains interact with XthA. The beta-clamp-XthA complex can be disrupted by clamp binding peptides and also by a specific bacterial clamp inhibitor that binds at the PBG. Addition of beta-clamp binding peptides disrupts the MtbXthA-clamp complex and inhibits clamp-dependent stimulation of MtbXthA, overview. The beta-clamp stimulates the activities of XthA primarily by increasing its affinity for the substrate and its processivity. Additionally, loading of the beta-clamp onto DNA is required for activity stimulation. In the absence of DNA, the PBG located on the second domain of the beta-clamp is important for interactions with XthA, while the C-terminal domain predominantly mediates functional interactions in the substrate's presence. The C-terminal domain of beta-clamp predominantly mediates interactions with XthA in the presence of DNA	-, 751601