EXOIII
SMART ACC:	SM000479
Description:	exonuclease domain in DNA-polymerase alpha and epsilon chain, ribonuclease T and other exonucleases
InterPro ACC:	IPR013520
InterPro abstract:	This entry includes a variety of exonuclease proteins, such as Oligoribonuclease, ribonuclease T [ PUBMED:8506149 ] and the epsilon subunit of DNA polymerase III. Ribonuclease T ( EC:3.1.13 ) is an enzyme found so far only in gamma-subdivision … expand This entry includes a variety of exonuclease proteins, such as Oligoribonuclease, ribonuclease T [ PUBMED:8506149 ] and the epsilon subunit of DNA polymerase III. Ribonuclease T ( EC:3.1.13 ) is an enzyme found so far only in gamma-subdivision proteobacteria such as Escherichia coli and Xylella fastidiosa. Ribonuclease T is homologous to the DNA polymerase III alpha chain. It can liberate AMP from the common C-C-A terminus of uncharged tRNA. It appears also to be involved in RNA maturation. It also acts as a 3' to 5' single-strand DNA-specific exonuclease; it is distinctive for its ability to remove residues near a double-stranded stem. Ribonuclease T is a high copy suppressor in E. coli of a UV-repair defect caused by deletion of three other single-stranded DNA exonucleases [ PUBMED:9857048 ]. Oligoribonuclease (Orn) is an essential 3'->5' exoribonuclease in Escherichia coli and other bacteria, specialising in the degradation of small oligoribonucleotides (2-5 nucleotides) to mononucleotides during mRNA decay. It ensures complete RNA turnover by hydrolysing these short RNA fragments, which accumulate lethally in its absence, disrupting cellular viability. Beyond mRNA processing, Orn plays a critical role in cyclic diguanylate (c-di-GMP) signalling by degrading the intermediate 5'-phosphoguanylyl-(3',5')-guanosine (pGpG), preventing its accumulation and subsequent inhibition of c-di-GMP phosphodiesterases. This activity regulates biofilm formation and virulence in pathogens like Pseudomonas aeruginosa. Structurally conserved across domains of life, Orn operates processively via a manganese-dependent mechanism, preferring substrates with free 3'-hydroxyl groups and exhibiting inverse activity dependence on oligomer length. Its dual role in RNA metabolism and signalling underscores its importance in maintaining cellular homeostasis [ PUBMED:10200269 PUBMED:26305928 PUBMED:9573169 ]. collapse
Family alignment:	View the Family alignment or the Alignment consensus sequence
There are 66 161 EXOIII domains in 66 129 proteins in SMART's NRDB database.

Taxonomic distribution of proteins containing EXOIII domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing EXOIII domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Predicted cellular role

Cellular role:	Replication

Relevant references for this domain

Primary literature for the EXOIII domain is listed below. Automatically-derived, secondary literature is also available.

KEGG pathways involving proteins which contain this domain

This information is based on the mapping of SMART genomic protein database to KEGG orthologous groups. Percentages are related to the number of proteins containing a EXOIII domain which could be assigned to a KEGG orthologous group, and not all proteins containing EXOIII domains. Please note that proteins can be included in multiple pathways, ie. the numbers below will not add to 100%.

KEGG pathways

Some of these pathways are included in the interactive Pathways Explorer overview maps. Select an overview map and click the button below to highlight them in iPath.

KEGG orthologous groups

Some of these KOs are included in the interactive Pathways Explorer overview maps. Select an overview map and click the button below to highlight them in iPath.

3D structures in PDB containing this domain

Links to other resources describing this domain

InterPro	IPR013520
Pfam	Exonuclease