DNA polymerase A type from plastids of higher plants possibly involve in DNA replication or in the repair of errors occurring during replication
DNA polymerase A type from plastids of higher plants possibly involve in DNA replication or in the repair of errors occurring during replication. Family A polymerase functions primarily to fill DNA gaps that arise during DNA repair, recombination and replication. DNA-dependent DNA polymerases can be classified in six main groups based upon phylogenetic relationships with E. coli polymerase I (classA), E. coli polymerase II (class B), E.coli polymerase III (class C), euryarchaaeota polymerase II (class D), human polymerase beta (class x), E. coli UmuC/DinB and eukaryotic RAP 30/Xeroderma pigmentosum variant (class Y). Family A polymerase are found primarily in organisms related to prokaryotes and include prokaryotic DNA polymerase I ,mitochondrial polymerase delta, and several bacteriphage polymerases including those from odd-numbered phage (T3, T5, and T7). The three-dimensional structure of plastid DNA polymerase has substantial similarity to Pol I. The structure of Pol I resembles in overall morphology a cupped human right hand, with fingers (which bind an incoming nucleotide and interact with the single-stranded template), palm (which harbors the catalytic amino acid residues and also binds an incoming dNTP) and thumb (which binds double-stranded DNA) subdomains.
Comment:The Pol A domain has a shape of a right hand in which the palm, fingers and thumb form the DNA-binding crevice; the active site, composed of three acidic residues, is located at the palm which forms the base of the crevice.