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At least 613 records · Page 34Linked to original sources
PubMed1991

A beta-galactosidase deletion mutant of Lactobacillus bulgaricus reverts to generate an active enzyme by internal DNA sequence duplication.

Several spontaneous Lac- deletion derivatives of the beta-galactosidase gene of Lactobacillus bulgaricus were analyzed for their phenotypic stability. We found that one of these mutants, lac139, carrying a deletion of 30 bp within the gene, was able to revert to a Lac+ phenotype. Genetical analysis of revertants indicated that an internal region of 72 bp was duplicated immediately next to the deletion site. The region involved in the duplication event is flanked by direct repeated sequences of 13 bp in length. Both events, the deletion and the duplication, were mediated by the presence of such short direct repeats. Enzymatic studies of the purified proteins indicated identical kinetic parameters, but showed considerable instability of the revertant protein.

Base Sequence↗
PubMed1980

Stimulation of Bacillus subtilis transformation by spermidine.

Addition of spermidine in millimolar concentrations to Bacillus subtilis cells curing competence development increases transformability. The spermidine must be added at least 30 min before DNA for maximum stimulation. An incubation period of about 30 minutes is also required for the maximum uptake of labeled spermidine. The amount of DNA initially attached and the rate of DNA uptake are increased to the same extent as transformation. The rate of protein synthesis is also equivalently increased. These observations are consistent with an increase in the number of competent cells in the cell population; this increase is mediated by a spermidine-stimulated protein synthesis.

Bacillus subtilis↗
PubMed1977

Macromolecular synthesis in chromosome initiation mutants of Bacillus subtilis.

Inactivation of the dna B or dna D gene product in Bacillus subtilis stimulates RNA and protein synthesis. Strains containing ts dna B and D mutations have been constructed by introducing the mutations by transformation into a thymine requiring strain which does not lyse during thymine starvation. The consequences of inactivation of these gene products have been assessed by comparing RNA and protein synthesis during thymine starvation at the restrictive temperature with the recipient strain. In the ts+ strain, there is a doubling in rate of RNA synthesis during thymine starvation. In the ts dna B and D mutations at the restrictive temperature the rate of RNA synthesis increases four fold. By preincubating the mutants in the absence of thymine for one generation at the permissive temperature the two fold increase in rate of RNA synthesis associated with inactivation of the initiation complex can be demonstrated under conditions where the ts+ strain shows a decrease in rate of RNA synthesis. The rate of protein synthesis observed largely reflects the rate of RNA synthesis in all strains. Completion of the chromosome at the restrictive temperature has no significant effect on the rate of RNA synthesis. It is suggested that inactivation of the initiation complex after chromosome initiation could play an important role in control of RNA synthesis in relation to the cell cycle.

Bacillus subtilis↗
PubMed1993

Excess histidine enzymes cause AICAR-independent filamentation in Escherichia coli.

High-level expression of the hisHAFI genes in Escherichia coli, cloned under the control of an IPTG-inducible promoter, caused filamentation, as previously reported in Salmonella typhimurium. We speculated that this filamentation might be produced by an action of the HisH and HisF enzymes on their product AICAR (amino-imidazole carboxamide riboside 5'-phosphate), a histidine by-product and normal purine precursor, possibly by favouring the formation of ZTP, the triphosphate derivative of AICAR. However, filamentation occurred even in the absence of carbon flow through the histidine and purine pathways, as observed in a hisG purF strain lacking the first enzyme in each pathway. Filamentation thus does not require either the normal substrate or products of the overproduced histidine enzymes and must reflect another activity.

Aminoimidazole Carboxamide↗
PubMed1992

ATPase activity of SopA, a protein essential for active partitioning of F plasmid.

The sopA, B, C genes of the F plasmid play an essential role in plasmid partitioning during cell division in Escherichia coli. In this paper, the products of the sopA and sopB genes were isolated and their biochemical activities studied. [alpha-32P]ATP was cross-linked to the SopA protein by UV irradiation; this cross-linking was observed only in the presence of magnesium ion, and was competitively inhibited in the presence of non-radioactive ATP, ADP and dATP, but not other NTPs or dNTPs. In contrast, no ATP binding activity was detected for the SopB protein. The SopA protein showed a modest magnesium ion-dependent ATPase activity and this activity was stimulated in the presence of DNA. The ATPase activity in the presence of DNA was further stimulated by addition of the SopB protein. However, the SopB protein alone failed to stimulate the ATPase activity.

Adenosine Triphosphatases↗
PubMed1983

Enzymatic formation of biparental figure-eight molecules from plasmid DNA and their resolution in E. coli.

A key intermediate in general genetic recombination is a structure in which two double-stranded DNA molecules are covalently linked by a single-strand crossover characteristic of a Holliday junction. When the DNA molecules are circular, the recombinant structures take the form of a figure eight. We have used purified E. coli enzymes to construct biparental figure-eight DNA molecules in vitro from the DNA of two partially homologous plasmids. When purified figure-eight structures are transfected into recA- E. coli cells, they are resolved to produce monomeric or dimeric plasmid progeny, apparently by the cutting and joining of the Holliday crossover. The maturation of figure-eight molecules in bacteria is characterized by the formation and recovery of both parental and recombinant types, cross-over at a frequency of up to 50% and the capability for mismatch repair at regions of hybrid DNA. In these three regards, the products of figure-eight maturation resemble recombinant chromosomes formed at meiosis. These observations show that biparental figure eights behave as recombination intermediates that can be resolved into mature recombinants without need for a functional recA+ gene product.

Bacterial Proteins↗
PubMed1998

CTG repeats show bimodal amplification in E. coli.

Trinucleotide repeats in human genetic disorders showing anticipation follow two inheritance patterns as a function of length. Inheritance of 35-50 repeats show incremental changes, while tracts greater than 80 repeats show large saltatory expansions. We describe a bacterial system that recapitulates this striking bimodal pattern of CTG amplification. Incremental expansions predominate in CTG tracts < Okazaki fragment size, while saltatory expansions increase in repeat tracts > or = Okazaki fragment size. CTG amplification requires loss of SbcC, a protein that modulates cleavage of single-stranded DNA and degradation of duplex DNA from double-strand breaks. These results suggest that noncanonical single strand-containing secondary structures in Okazaki fragments and/or double-strand breaks in repeat tracts are intermediates in CTG amplification.

Bacterial Proteins↗