This is a conserved region from DNA primase. This corresponds to the Toprim domain common to DnaG primases, topoisomerases, OLD family nucleases and RecR proteins [1]. Both DnaG motifs IV and V are present in the alignment, the DxD (V) motif may be involved in Mg2+ binding and mutations to the conserved glutamate (IV) completely abolish DnaG type primase activity [1]. DNA primase EC:2.7.7.6 is a nucleotidyltransferase it synthesises the oligoribonucleotide primers required for DNA replication on the lagging strand of the replication fork; it can also prime the leading stand and has been implicated in cell division [2]. This family also includes the atypical archaeal A subunit from type II DNA topoisomerases [4]. Type II DNA topoisomerases catalyse the relaxation of DNA supercoiling by causing transient double strand breaks.

1: Toprim--a conserved catalytic domain in type IA and II topoisomerases, DnaG-type primases, OLD family nucleases and RecR proteins. Aravind L, Leipe DD, Koonin EV; Nucleic Acids Res 1998;26:4205-4213. PMID:9722641

2: Cloning and analysis of the dnaG gene encoding Pseudomonas putida DNA primase. Szafranski P, Smith CL, Cantor CR; Biochim Biophys Acta 1997;1352:243-248. PMID:9224947

3: The Haemophilus influenzae dnaG sequence and conserved bacterial primase motifs. Versalovic J, Lupski JR; Gene 1993;136:281-286. PMID:8294018

4: An atypical topoisomerase II from Archaea with implications for meiotic recombination. Bergerat A, de Massy B, Gadelle D, Varoutas PC, Nicolas A, Forterre P; Nature 1997;386:414-417. PMID:9121560