| Type: | Domain | Name: | DNA-directed DNA polymerase, family B, exonuclease domain |
| Description: | DNA is 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 life cycle of a cell. This function is performed by DNA- directed DNA-polymerases ) by adding nucleotide triphosphate (dNTP) residues to the 5'-end of the growing chain of DNA, using a complementary DNAchain as a template. Small RNA molecules are generally used as primers for chain elongation, although terminal proteins may also be used for the de novo synthesis of a DNA chain. Even though there are 2 different methods of priming, these aremediated by 2 very similar polymerases classes, A and B, with similar methods of chain elongation. A number of DNA polymerases have been grouped under the designation of DNA polymerase family B. Six regionsof similarity (numbered from I to VI) are found in all or a subset of the B family polymerases. The most conserved region (I) includes a conserved tetrapeptide with two aspartate residues. Its function is not yet known. However, it has been suggestedthat it may be involved in binding a magnesium ion. All sequences in the B family contain a characteristic DTDS motif, and possess many functional domains, including a 5'-3' elongation domain, a 3'-5' exonuclease domain [], a DNA binding domain,and binding domains for both dNTP's and pyrophosphate []. This domain has 3' to 5' exonuclease activity and adopts a ribonuclease H type fold []. | Short Name: | DNA-dir_DNA_pol_B_exonuc |
