InterPro domain: IPR006172

DNA is the biological information that instructs cells how to exist in anordered fashion: accurate replication is thus one of the most importantevents in the life cycle of a cell. This function is performed by DNA-directed DNA-polymerases ( 2.7.7.7 ) 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 groupedunder the designation of DNA polymerase family B.Six regions of similarity (numbered from I to VI) are found in all or a subsetof the B family polymerases. The most conserved region (I) includes a conservedtetrapeptide with two aspartate residues. Its function is not yet known.However, it has been suggested [ 1 ] that it may be involved in binding amagnesium ion. All sequences in the Bfamily contain a characteristic DTDS motif, and possess many functionaldomains, including a 5'-3' elongation domain, a 3'-5' exonuclease domain [ 2 ],a DNA binding domain, and binding domains for both dNTP's and pyrophosphate [ 3 ].

1. A sequence motif in many polymerases. Nucleic Acids Res. 16, 9909-16
2. Crystal structures of an NH2-terminal fragment of T4 DNA polymerase and its complexes with single-stranded DNA and with divalent metal ions. Biochemistry 35, 8110-9
3. Crystallization and preliminary diffraction analysis of a hyperthermostable DNA polymerase from a Thermococcus archaeon. Acta Crystallogr. D Biol. Crystallogr. 54, 994-5