| Primary Identifier | IPR042087 | Type | Homologous_superfamily |
| Short Name | DNA_pol_B_thumb |
| 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 DNA chain 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 are mediated 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 regions of 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 suggested that 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 []. The DNA polymerase structure resembles a right hand with fingers, palm, and thumb, with an active site formed by a palm holding the catalytic residues, a thumb that binds the primer:template DNA and fingers interacting with incoming nucleotide, and the N and Exo domains extend from the finger toward the thumb [, , ].This superfamily represents the thumb domain found at the C-terminal of the DNA polymerase family B proteins. |
