Escherichia coli DnaX product, the tau subunit of DNA polymerase III, is a multifunctional protein with single-stranded DNA-dependent ATPase activity.

ABSTRACT The Escherichia coli DNA polymerase III τ and γ subunits are single-strand DNA-dependent ATPases (the latter requires the δ and δ′ subunits for significant ATPase activity) involved in loading processivity clamp β. They are homologous to clamp-loading proteins of many organisms from phages to humans. Alignment of 27 prokaryotic τ/γ homologs and 1 eukaryotic τ/γ homolog has refined the sequences of nine previously defined identity and functional motifs. Mutational analysis has defined highly conserved residues required for activity in vivo and in vitro. Specifically, mutations introduced into highly conserved residues within three of those motifs, the P loop, the DExx region, and the SRC region, inactivated complementing activity in vivo and clamp loading in vitro and reduced ATPase catalytic efficiency in vitro. Mutation of a highly conserved residue within a fourth motif, VIc, inactivated clamp-loading activity and reduced ATPase activity in vitro, but the mutant gene, on a multicopy plasmid, retained complementing activity in vivo and the mutant gene also supported apparently normal replication and growth as a haploid, chromosomal allele.

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Mechanism of replication of ultraviolet-irradiated single-stranded DNA by DNA polymerase III holoenzyme of Escherichia coli. Implications for SOS mutagenesis.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)67689-6 ◽

1986 ◽

Vol 261 (20) ◽

pp. 9526-9533

Author(s):

Z Livneh

Keyword(s):

Escherichia Coli ◽

Dna Polymerase ◽

Dna Polymerase Iii ◽

Single Stranded Dna ◽

Sos Mutagenesis ◽

Polymerase Iii

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Replication of UV-irradiated single-stranded DNA by DNA polymerase III holoenzyme of Escherichia coli: evidence for bypass of pyrimidine photodimers.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.83.13.4599 ◽

1986 ◽

Vol 83 (13) ◽

pp. 4599-4603 ◽

Cited By ~ 31

Author(s):

Z. Livneh

Keyword(s):

Escherichia Coli ◽

Dna Polymerase ◽

Dna Polymerase Iii ◽

Single Stranded Dna ◽

Polymerase Iii

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E. coli primase and DNA polymerase III holoenzyme are able to bind concurrently to a primed template during DNA replication

Scientific Reports ◽

10.1038/s41598-019-51031-0 ◽

2019 ◽

Vol 9 (1) ◽

Author(s):

Andrea Bogutzki ◽

Natalie Naue ◽

Lidia Litz ◽

Andreas Pich ◽

Ute Curth

Keyword(s):

Dna Replication ◽

Dna Polymerase ◽

Protein Interactions ◽

Dna Polymerase Iii ◽

Protein Protein Interactions ◽

Single Stranded Dna ◽

E Coli ◽

Polymerase Iii ◽

C Terminus ◽

Pol Iii

Abstract During DNA replication in E. coli, a switch between DnaG primase and DNA polymerase III holoenzyme (pol III) activities has to occur every time when the synthesis of a new Okazaki fragment starts. As both primase and the χ subunit of pol III interact with the highly conserved C-terminus of single-stranded DNA-binding protein (SSB), it had been proposed that the binding of both proteins to SSB is mutually exclusive. Using a replication system containing the origin of replication of the single-stranded DNA phage G4 (G4ori) saturated with SSB, we tested whether DnaG and pol III can bind concurrently to the primed template. We found that the addition of pol III does not lead to a displacement of primase, but to the formation of higher complexes. Even pol III-mediated primer elongation by one or several DNA nucleotides does not result in the dissociation of DnaG. About 10 nucleotides have to be added in order to displace one of the two primase molecules bound to SSB-saturated G4ori. The concurrent binding of primase and pol III is highly plausible, since even the SSB tetramer situated directly next to the 3′-terminus of the primer provides four C-termini for protein-protein interactions.

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