ATPase/helicase motif mutants of Escherichia coli PriA protein essential for recombination-dependent DNA replication.
BACKGROUND
PriA protein, a DEXH-type helicase with C2C2 zinc-finger motifs, plays essential roles in RecA-dependent modes of Escherichia coli chromosomal DNA replication, namely inducible and constitutive stable DNA replication (iSDR and cSDR respectively, which may be initiated from a D-loop or R-loop structure), and in repair of double-stranded DNA breaks generated by various genotoxic agents or spontaneously during the course of DNA replication. However, the roles of ATPase/DNA helicase activities in functions of PriA are not well understood.


RESULTS
We have generated and characterized mutants of PriA protein carrying amino acid substitutions in its conserved ATPase/DNA helicase motifs, namely the Walker A, B and QXXGRXGR motifs. All these mutants were deficient in ATP hydrolysis and DNA helicase activities, but showed wild-type levels of D-loop DNA binding, except for the Walker B mutant which showed reduced DNA binding activity, suggesting that the helicase motifs are not directly involved in the DNA binding activity of PriA protein. They also rescued the low viability and UV-sensitivity of priA null cells. However, they did not rescue iSDR or cSDR-alternative modes of chromosomal DNA replication of the E. coli genome dependent on recombination functions-to the full extent.


CONCLUSIONS
ATPase/DNA helicase activities of PriA protein are required for full-level DNA synthesis in recombination-dependent modes of DNA replication in E. coli.
Tanaka
Taku
T
Department of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan.
Taniyama
Chika
C
Arai
Ken-Ichi
K
Masai
Hisao
H
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D020816:Amino Acid Motifs / Q000235:genetics / Q000502:physiology; D004247:DNA / Q000378:metabolism; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D009154:Mutation; D051716:Replication Protein A; D013329:Structure-Activity Relationship
D004268:DNA-Binding Proteins; D051716:Replication Protein A; D004247:DNA; D000251:Adenosine Triphosphatases; D004265:DNA Helicases