PcrA is an essential DNA helicase of Bacillus subtilis fulfilling functions both in repair and rolling‐circle replication

• Published in: Molecular microbiology 1998-07, Vol.29 (1), p.261-273
• Main Authors: Petit, Marie‐Agnès, Dervyn, Etienne, Rose, Matthias, Entian, Karl‐Dieter, McGovern, Steven, Ehrlich, S. Dusko, Bruand, Claude
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - genetics; Amino Acid Sequence; Bacillus subtilis - genetics; Bacillus subtilis - growth & development; Bacillus subtilis - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Cell Division; DNA Helicases - genetics; DNA Helicases - metabolism; DNA Repair; DNA Replication; DNA, Bacterial; DnaB Helicases; Escherichia coli - genetics; Escherichia coli - physiology; Escherichia coli Proteins; Genes, Bacterial; Life Sciences; Microbiology and Parasitology; Molecular Sequence Data; Mutation; Plasmids
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1046/j.1365-2958.1998.00927.x

The only DNA helicase essential for Escherichia coli viability is DnaB, the chromosome replication fork helicase. In contrast, in Bacillus subtilis, in addition to the DnaB counterpart called DnaC, we have found a second essential DNA helicase, called PcrA. It is 40% identical to the Rep and UvrD DNA helicases of E. coli and 61% identical to the PcrA helicase of Staphylococcus aureus. This gene is located at 55° on the chromosome and belongs to a putative operon together with a ligase gene (lig ) and two unknown genes named pcrB and yerH. As PcrA was essential for cell viability, conditional mutants were constructed. In such mutants, chromosomal DNA synthesis was slightly decreased upon PcrA depletion, and rolling‐circle replication of the plasmid pT181 was inhibited. Analysis of the replication intermediates showed that leading‐strand synthesis of pT181 was prevented upon PcrA depletion. To compare PcrA with Rep and UvrD directly, the protein was produced in rep and uvrD mutants of E. coli. PcrA suppressed the UV sensitivity defect of a uvrD mutant but not its mutator phenotype. Furthermore, it conferred a Rep− phenotype on E. coli. Altogether, these results show that PcrA is an helicase used for plasmid rolling‐circle replication and suggest that it is also involved in UV repair.