Polymerase and Histidinol Phosphatase domain of alpha-subunit of bacterial polymerase III at DnaE2 gene
PolIIIA DnaE2 plays a role in SOS mutagenesis/translesion synthesis and has dominant effects in determining GC variability in the bacterial genome. PolIIIAs that contain an N-terminal PHP domain have been classified into four basic groups based on genome composition, phylogenetic, and domain structural analysis: polC, dnaE1, dnaE2, and dnaE3. The PHP (also called histidinol phosphatase-2/HIS2) domain is associated with several types of DNA polymerases, such as PolIIIA and family X DNA polymerases, stand alone histidinol phosphate phosphatases (HisPPases), and a number of uncharacterized protein families. DNA polymerase III holoenzyme is one of the five eubacterial DNA polymerases that are responsible for the replication of the DNA duplex. PolIIIA core enzyme catalyzes the reaction for polymerizing both DNA strands. PolC PHP is located in a different location compared to dnaE1, 2, and 3. dnaE1 is the longest compared to dnaE2 and dnaE3. A unique motif was also identified in dnaE1 and dnaE3 genes. The PHP domain has four conserved sequence motifs and contains an invariant histidine that is involved in metal ion coordination. PHP domains found in DnaEs of thermophilic origin exhibit 3'-5' exonuclease activity.
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