The ssb‐113 allele suppresses the dnaQ49 mutator and alters DNA supercoiling in Escherichia coli

Quiñones, Ariel; Neumann, Susanne

doi:10.1046/j.1365-2958.1997.4531718.x

Cited by 6 publications

(4 citation statements)

References 57 publications

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“…SSB, possibly by virtue of its ability to stabilize the single-stranded regions in DNA, stimulates the enzyme activity. Support for this functional cooperation between topoisomerase I and SSB also comes from studies where an SSB allele is shown to influence DNA supercoiling levels in the cells (41). One would expect increased local concentration of both topoisomerase I and SSB at regions of DNA actively involved in replication process.…”

Section: Discussionmentioning

confidence: 92%

DNA Topoisomerase I from Mycobacterium smegmatis

Bhaduri¹,

Bagui²,

Sikder

et al. 1998

Journal of Biological Chemistry

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A type I topoisomerase has been purified to homogeneity from Mycobacterium smegmatis. It is the largest single subunit enzyme of this class having molecular mass of 110 kDa. The enzyme is Mg 2؉ dependent and can relax negatively supercoiled DNA, catenate, and knot single-stranded DNA, thus having typical properties of type I topoisomerases. Furthermore, the enzyme makes single-stranded nicks and the 5-phosphoryl end of the nicked DNA gets covalently linked with a tyrosine residue of the enzyme. However, M. smegmatis enzyme shows some distinctive features from the prototype Escherichia coli topoisomerase I. The enzyme is relatively stable at higher temperatures and not inhibited by spermidine. It apparently does not contain any bound Zn 2؉ and on modification of cysteine residues retains the activity, suggesting the absence of the zincfinger motif in DNA binding. Partially purified Mycobacterium tuberculosis topoisomerase I exhibits very similar properties with respect to size, stability, and reaction characteristics. Sequence comparison of topoisomerase I from E. coli and M. tuberculosis shows the absence of zinc-finger motifs in mycobacterial enzyme. Using a two-substrate assay system, we demonstrate that the enzyme acts processively at low ionic strength and switches over to distributive mode at high Mg 2؉ concentration. Significantly, the enzyme activity is stimulated by single strand DNA-binding protein. There is a potential to exploit the characteristics of the enzyme to develop it as a molecular target against mycobacterial infections.

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Section: Discussionmentioning

confidence: 92%

DNA Topoisomerase I from Mycobacterium smegmatis

Bhaduri¹,

Bagui²,

Sikder

et al. 1998

Journal of Biological Chemistry

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“…This mechanism is based on the concept which was "rst proposed by Scheuermann and Echols (1984), and some evidence supporting it can be seen (e.g. Fujita et al, 1987;Foster & Marinus, 1992;Quinones & Neumann, 1997). In the DNA polymerase of Gram-positive bacteria, in contrast, both DNA synthesis and proofreading activities exist on a single polypeptide (Kornberg & Baker, 1992).…”

Section: Discussionmentioning

confidence: 97%

Promotion of Evolution by Intracellular Coexistence of Mutator and Normal DNA Polymerases

Aoki

Furusawa²

2001

Journal of Theoretical Biology

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“…26 The interaction between SSB and χ is critical as mutations within the protein interaction domain in SSB (e.g., ssb-113 ) are conditionally lethal. 27 Furthermore, strand displacement synthesis catalyzed by the Pol III HE in the absence of helicase is dependent on SSB. 28 SSB directly interacts with primase (DnaG) 29; 30 as well as with PriA.…”

Section: Introductionmentioning

confidence: 99%

Multiple C-Terminal Tails within a Single E. coli SSB Homotetramer Coordinate DNA Replication and Repair

Antony

Weiland

Yuan

et al. 2013

Journal of Molecular Biology

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E. coli single strand DNA binding protein (SSB) plays essential roles in DNA replication, recombination and repair. SSB functions as a homotetramer with each subunit possessing a DNA binding domain (OB-fold) and an intrinsically disordered C-terminus, of which the last nine amino acids provide the site for interaction with at least a dozen other proteins that function in DNA metabolism. To examine how many C-termini are needed for SSB function we engineered covalently linked forms of SSB that possess only one or two C-termini within a four OB-fold “tetramer”. Whereas E. coli expressing SSB with only two tails can survive, expression of a single tailed SSB is dominant lethal. E. coli expressing only the two-tailed SSB recovers faster from exposure to DNA damaging agents, but accumulate more mutations. A single-tailed SSB shows defects in coupled leading and lagging strand DNA replication and does not support replication restart in vitro. These deficiencies in vitro provide a plausible explanation for the lethality observed in vivo. These results indicate that a single SSB tetramer must interact simultaneously with multiple protein partners during some essential roles in genome maintenance.

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The ssb‐113 allele suppresses the dnaQ49 mutator and alters DNA supercoiling in Escherichia coli

Cited by 6 publications

References 57 publications

DNA Topoisomerase I from Mycobacterium smegmatis

DNA Topoisomerase I from Mycobacterium smegmatis

Promotion of Evolution by Intracellular Coexistence of Mutator and Normal DNA Polymerases

Multiple C-Terminal Tails within a Single E. coli SSB Homotetramer Coordinate DNA Replication and Repair

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