DNA-directed DNA polymerase, family B, exonuclease domain QuickView

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. This domain is the exonuclease domain of family B DNA polymerases. It adopts a ribonuclease H type fold.

QuickView for DNA-directed DNA polymerase, family B, exonuclease domain (biogroup)