POLXc DNA polymerase X family
SMART ACC:	SM000483
Description:	includes vertebrate polymerase beta and terminal deoxynucleotidyltransferases
InterPro ACC:	IPR002054
InterPro abstract:	DNA carries the biological information that instructs cells how to exist in an ordered fashion: accurate replication is thus one of the most important events in the cell life cycle. This function is mediated by DNA-directed DNA-polymerases, which add nucleotide triphosphate (dNTP) residues to the 5'-end of the growing DNA chain, using a complementary DNA as template. Small RNA molecules are generally … expand DNA carries the biological information that instructs cells how to exist in an ordered fashion: accurate replication is thus one of the most important events in the cell life cycle. This function is mediated by DNA-directed DNA-polymerases, which add nucleotide triphosphate (dNTP) residues to the 5'-end of the growing DNA chain, using a complementary DNA as template. Small RNA molecules are generally used as primers for chain elongation, although terminal proteins may also be used. Three motifs, A, B and C [ PUBMED:2196557 ], are seen to be conserved across all DNA-polymerases, with motifs A and C also seen in RNA- polymerases. They are centred on invariant residues, and their structural significance was implied from the Klenow (Escherichia coli) structure: motif A contains a strictly-conserved aspartate at the junction of a β-strand and an α-helix; motif B contains an α-helix with positive charges; and motif C has a doublet of negative charges, located in a β-turn-β secondary structure [ PUBMED:2196557 ]. DNA polymerases ( EC:2.7.7.7 ) can be classified, on the basis of sequence similarity [ PUBMED:3479792 PUBMED:2196557 ], into at least four different groups: A, B, C and X. X family polymerases fill in short gaps during DNA repair, and are small (about 40kDa) compared with other polymerases. They are relatively inaccurate enzymes and play roles in base excision repair, in non-homologous end joining (NHEJ) which acts mainly to repair damage due to ionizing radiation, and in V(D)J recombination [ PUBMED:16061182 PUBMED:15100289 ]. X family polymerases include eukaryotic Pol beta, Pol lambda, Pol mu and terminal deoxynucleotidyl-transferase (TdT) ( EC:2.7.7.31 ). Pol beta and Pol lambda are primarily DNA template-dependent polymerases, whereas TdT is a DNA template-independent polymerase [ PUBMED:18972388 ]. Pol mu has both template dependent and template independent activities [ PUBMED:17159995 ]. These enzymes catalyse addition of nucleotides in a distributive manner, i.e. they dissociate from the template-primer after addition of each nucleotide. DNA-polymerases show a degree of structural similarity with RNA-polymerases. This domain is found either at the extreme N or C termini of DNA polymerase X proteins. collapse
GO function:	DNA binding (GO:0003677), DNA-directed DNA polymerase activity (GO:0003887)
Family alignment:	View the Family alignment or the Alignment consensus sequence
There are 6 622 POLXc domains in 6 621 proteins in SMART's NRDB database.

Taxonomic distribution of proteins containing POLXc domains

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

Relevant references for this domain

Primary literature for the POLXc 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 POLXc domain which could be assigned to a KEGG orthologous group, and not all proteins containing POLXc 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

PROSITE	DNA_POLYMERASE_X
InterPro	IPR002054
Pfam	DNA_polymeraseX