Requirement for ubiquinone downstream of cytochrome(s) b in the oxygen-terminated respiratory chains of Escherichia coli K-12 revealed using a null mutant allele of ubiCA

Abstract First identified as an essential component of the ϕX174 in vitro DNA replication system, PriA has ATPase, helicase, translocase, and primosome-assembly activities. priA1::kan strains of Escherichia coli are sensitive to UV irradiation, deficient in homologous recombination following transduction, and filamentous. priA2::kan strains have eightfold higher levels of uninduced SOS expression than wild type. We show that (1) priA1::kan strains have eightfold higher levels of uninduced SOS expression, (2) priA2::kan strains are UVS and Rec−, (3) lexA3 suppresses the high basal levels of SOS expression of a priA2::kan strain, and (4) plasmid-encoded priA300 (K230R), a mutant allele retaining only the primosome-assembly activity of priA+, restores both UVR and Rec+ phenotypes to a priA2::kan strain. Finally, we have isolated 17 independent UVR Rec+ revertants of priA2::kan strains that carry extragenic suppressors. All 17 map in the C-terminal half of the dnaC gene. DnaC loads the DnaB helicase onto DNA as a prelude for primosome assembly and DNA replication. We conclude that priA's primosome-assembly activity is essential for DNA repair and recombination and that the dnaC suppressor mutations allow these processes to occur in the absence of priA.

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Positive control of sulphate reduction in Escherichia coli. The nature of the pleiotropic cysteineless mutants of E. coli K 12

Biochemical Journal ◽

10.1042/bj1100597 ◽

1968 ◽

Vol 110 (3) ◽

pp. 597-602 ◽

Cited By ~ 21

Author(s):

M. C. Jones-Mortimer

Keyword(s):

Escherichia Coli ◽

Mutant Allele ◽

Positive Control ◽

Wild Type Allele ◽

Wild Type ◽

E Coli ◽

Type Allele ◽

K 12 ◽

Sulphite Reductase

1. The function of the wild-type alleles of the pleiotropic mutants cysB and cysE of Escherichia coli was investigated. 2. The wild-type allele cysB+ is dominant to the mutant allele cysB in stable and transient heterozygotes. 3. The wild-type allele cysE+ is dominant to the mutant allele cysE, as predicted. 4. Sulphur-starved cultures of cysB or cysE strains contain less than 0·2nmole of free cysteine/mg. dry wt. 5. Complementation in vitro is not observed between extracts of cysB mutants and mutants lacking sulphite reductase only. 6. A scheme, involving positive control of the enzymes of sulphate activation and reduction, is suggested to account for the control of cysteine biosynthesis.

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The Periplasmic Murein Peptide-Binding Protein MppA Is a Negative Regulator of Multiple Antibiotic Resistance in Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.181.16.4842-4847.1999 ◽

1999 ◽

Vol 181 (16) ◽

pp. 4842-4847 ◽

Cited By ~ 16

Author(s):

HongShan Li ◽

James T. Park

Keyword(s):

Escherichia Coli ◽

Antibiotic Resistance ◽

Binding Protein ◽

Wide Spectrum ◽

Negative Regulator ◽

Null Mutant ◽

Multiple Antibiotic Resistance ◽

Resistance Phenotype ◽

E Coli ◽

K 12

ABSTRACT MppA is a periplasmic binding protein in Escherichia coli essential for uptake of the cell wall murein tripeptidel-alanyl-γ-d-glutamyl-meso-diaminopimelate. We have found serendipitously that E. coli K-12 strains carrying a null mutation in mppA exhibit increased resistance to a wide spectrum of antibiotics and to cyclohexane. Normal sensitivity of the mppA mutant to these agents is restored by mppA expressed from a plasmid. As is observed in the multiple antibiotic resistance phenotype in E. coli cells, the mppA null mutant overproduces the transcriptional activator, MarA, resulting in expression of the membrane-bound AcrAB proteins that function as a drug efflux pump. Reduced production of OmpF similar to that observed in the multiple antibiotic resistance phenotype is also seen in the mppA mutant. These and other data reported herein indicate that MppA functions upstream of MarA in a signal transduction pathway to negatively regulate the expression ofmarA and hence of the MarA-driven multiple antibiotic resistance. Overproduction of cytoplasmic GadA and GadB and of several unidentified cytoplasmic membrane proteins as well as reduction in the amount of the outer membrane protein, OmpP, in the mppAnull mutant indicate that MppA regulates a number of genes in addition to those already known to be controlled by MarA.

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