The influence of radiomimetic substances on deoxyribonucleic acid synthesis and function studied in Escherichia coli / phage systems - III. Mutation of T 2 bacteriophage as a consequence of alkylation in vitro : the uniqueness of ethylation

1959 ◽  
Vol 150 (941) ◽  
pp. 497-508 ◽  
Keyword(s):  
Escherichia Coli ◽  
Burst Size ◽  
Alkylating Agents ◽  
Direct Consequence ◽  
Acid Synthesis ◽  
Deoxyribonucleic Acid Synthesis ◽  
Methane Sulphonate ◽  
Average Burst Size ◽  
And Function

Of a comprehensive set of alkylating agents tested, only two, namely, ethyl methane sulphonate and diethyl sulphate, have been found so to interact with T 2 bacteriophage that cells of Escherichia coli , infected with phage treated extracellularly, manifest a considerably increased likelihood of yielding mutated phage. Since this increase can occur where the infective titre of the phage and the latent period and average burst size of the infected bacteria remain unchanged, it is considered that the increased mutation rate is a direct consequence of the chemical treatment, although the alkylation itself does not constitute the mutation. A study of the manner of inactivation of the phage by these agents has not revealed any characteristic difference between ethylation and other alkylations which could be held to account for its apparent uniqueness.

The influence of radiomimetic substances on deoxyribonucleic acid synthesis and function studied in Escherichia coli / phage systems V. A comparison of the inactivation of phages T 2, T 7 and two strains of T 4 by alkylating agents

1959 ◽  
Vol 151 (942) ◽  
pp. 148-155 ◽  
Keyword(s):  
Deoxyribonucleic Acid ◽  
Osmotic Shock ◽  
Alkylating Agents ◽  
Acid Synthesis ◽  
Acid Moiety ◽  
Rate Of Penetration ◽  
Injection Process ◽  
Deoxyribonucleic Acid Synthesis ◽  
And Function ◽  
Escherichia Coli Phage

The sensitivity of phage T 7 to epoxides and freshly prepared solutions of di(2-chloroethyl) methylamine ( HN 2) was identical with that of T 2. T 7, however, proved considerably the more sensitive to ethylenimine and to aged solutions of HN 2. It was considered that this was due to the cationic nature of these latter agents affecting the rate of penetration into the phage heads, and that the susceptibility of T 2 and resistance of T 7 to osmotic shock was a parallel phenomenon. Confirmation was afforded by the fact that a strain of T 4 sensitive to osmotic shock behaved like T 2, and a resistant strain of T 4 like T 7. These results, together with others previously reported, are believed to offer very strong evidence that inactivation of bacteriophage by alkylating agents derives from reaction with the deoxyribonucleic acid moiety, probably leading to a failure of the injection process.

The influence of radiomimetic substances on deoxyribonucleic acid synthesis and function studied in escherichia coli/phage systems - IV. Colony-forming ability and escherichia coli strain B and two of its mutants following alkylation

1959 ◽  
Vol 151 (942) ◽  
pp. 129-147 ◽  
Keyword(s):  
Escherichia Coli ◽  
Chemical Reactivity ◽  
Alkylating Agents ◽  
Chemical Change ◽  
Acid Synthesis ◽  
Coli Strain ◽  
Ribonucleic Acids ◽  
Significant Difference ◽  
Synthetic Capacity ◽  
And Function

Escherichia coli strain B , its mutant B/r and a new mutant, designated B/HN 2, have been employed in a study of the effect of alkylating agents upon the survival of colony-forming ability and phage-synthetic capacity. This has been done against the background of our earlier work upon phage and that of other workers upon bacteria, employing both alkylating agents and radiations. The sensitivity of B toward all the compounds now studied was greater than that of the other two strains as regards colony-forming ability, whereas all three strains showed a similar sensitivity in regard to capacity. Survival curves of all strains treated with monofunctional agents were of a so-called ‘multi-hit’ type, whereas those for bifunctional compounds were downwardly concave. The response to di(2-ehloroethyl) methylamine ( HN 2) was complicated by the chemical change undergone by this substance in aqueous solution, as was shown by a comparison of fresh and aged solutions and of the effect of different cultural conditions prior to treatment. As with radiations, phage-synthetic capacity was considerably less sensitive to alkylation than colony-forming ability, whilst this sensitivity was essentially the same for the three strains. No significant difference was found between the effect of HN 2 on the capacity of B for T 2 and for T 7. The capacity of B/r for T 2 was more sensitive to treatment by a bifunctional agent than by a monofunctional agent of similar chemical reactivity. It is suggested that this may implicate ribonucleic acids as the reactive substrate essential to capacity.

Nonrandom substitution of 2-aminopurine for adenine during deoxyribonucleic acid synthesis in vitro

Biochemistry ◽  
1981 ◽  
Vol 20 (21) ◽  
pp. 6235-6244 ◽  
Author(s):  
Reynaldo C. Pless ◽  
Lore M. Levitt ◽  
Maurice J. Bessman
Keyword(s):  
Deoxyribonucleic Acid ◽  
Acid Synthesis ◽  
Deoxyribonucleic Acid Synthesis

scholarly journals Mutational Analysis of Residues in PriA and PriC Affecting Their Ability To Interact with SSB in Escherichia coli K-12

2020 ◽  
Vol 202 (23) ◽  
Author(s):  
Anastasiia N. Klimova ◽  
Steven J. Sandler
Keyword(s):  
Escherichia Coli ◽  
Mutational Analysis ◽  
Wild Type ◽  
Content Type ◽  
Growth Defects ◽  
C Terminus ◽  
K 12 ◽  
And Function

ABSTRACT Escherichia coli PriA and PriC recognize abandoned replication forks and direct reloading of the DnaB replicative helicase onto the lagging-strand template coated with single-stranded DNA-binding protein (SSB). Both PriA and PriC have been shown by biochemical and structural studies to physically interact with the C terminus of SSB. In vitro, these interactions trigger remodeling of the SSB on ssDNA. priA341(R697A) and priC351(R155A) negated the SSB remodeling reaction in vitro. Plasmid-carried priC351(R155A) did not complement priC303::kan, and priA341(R697A) has not yet been tested for complementation. Here, we further studied the SSB-binding pockets of PriA and PriC by placing priA341(R697A), priA344(R697E), priA345(Q701E), and priC351(R155A) on the chromosome and characterizing the mutant strains. All three priA mutants behaved like the wild type. In a ΔpriB strain, the mutations caused modest increases in SOS expression, cell size, and defects in nucleoid partitioning (Par−). Overproduction of SSB partially suppressed these phenotypes for priA341(R697A) and priA344(R697E). The priC351(R155A) mutant behaved as expected: there was no phenotype in a single mutant, and there were severe growth defects when this mutation was combined with ΔpriB. Analysis of the priBC mutant revealed two populations of cells: those with wild-type phenotypes and those that were extremely filamentous and Par− and had high SOS expression. We conclude that in vivo, priC351(R155A) identified an essential residue and function for PriC, that PriA R697 and Q701 are important only in the absence of PriB, and that this region of the protein may have a complicated relationship with SSB. IMPORTANCE Escherichia coli PriA and PriC recruit the replication machinery to a collapsed replication fork after it is repaired and needs to be restarted. In vitro studies suggest that the C terminus of SSB interacts with certain residues in PriA and PriC to recruit those proteins to the repaired fork, where they help remodel it for restart. Here, we placed those mutations on the chromosome and tested the effect of mutating these residues in vivo. The priC mutation completely abolished function. The priA mutations had no effect by themselves. They did, however, display modest phenotypes in a priB-null strain. These phenotypes were partially suppressed by SSB overproduction. These studies give us further insight into the reactions needed for replication restart.

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