Ubiquinone and vitamin K in bacteria

Bishop, David H. L.; Pandya, K. P.; King, H. K.

doi:10.1042/bj0830606

Cited by 182 publications

(88 citation statements)

References 14 publications

(5 reference statements)

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“…distinct regulatory genes. The oxrA gene (39), equivalent to thefnr gene of Escherichia coli (9,25,28), encodes a protein that positively controls a number of genes in S. typhimurium, including some terminal reductases (4,9,25,38). The oxrB gene product is involved in anaerobic expression of the oxrA-dependent genes (39).…”

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confidence: 99%

Redox regulation of the genes for cobinamide biosynthesis in Salmonella typhimurium

Andersson

Roth

1989

J Bacteriol

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Transcription of the cobinamide biosynthetic genes (the CobI operon) was induced under three different physiological conditions: anaerobiosis (anaerobic respiration or fermentation), aerobic respiration at low oxygen levels, and aerobic respiration with a partial block of the electron transport chain. After a shift to inducing conditions, there was a time lag of approximately 50 min before the onset of CobI induction. Under conditions of anaerobic respiration, the level of CobI transcription was dependent on the nature of both the electron donor (carbon and energy source) and the acceptor. Cells grown with electron acceptors with a lower midpoint potential showed higher CobI expression levels. The highest level of CobI transcription observed was obtained with glycerol as the carbon source and fumarate as the electron acceptor. The high induction seen with glycerol was reduced by mutational blocks in the glycerol catabolic pathway, suggesting that glycerol does not serve as a gratuitous inducer but must be metabolized to stimulate CobI transcription. In the presence of oxygen, CobI operon expression was induced 6-to 20-fold by the following: inhibition of cytochrome o oxidase with cyanide, mutational blockage of ubiquinone biosynthesis, and starvation of mutant cells for heme. We suggest that the CobI operon is induced in response to a reducing environment within the cell and not by the absence of oxygen per se.The B12 biosynthetic genes are organized into three functionally related gene clusters located at 41 min on the chromosome (19,20); all genes are transcribed counterclockwise and appear to comprise three operons. The CobI operon encodes cobinamide biosynthetic functions, the CoblI operon encodes dimethyl benzimidazole biosynthesis, and the CobIII operon encodes functions required to join cobinamide and dimethyl benzimidazole, forming cobalamin. Most B12 biosynthetic genes appear to be included in these three operons. It was established by Jeter et al. (19) that de novo biosynthesis of vitamin B12 in Salmonella typhimurium occurs only under anaerobic growth conditions. Under aerobic conditions, S. typhimurium can make B12 if provided with cobinamide, suggesting that only synthesis and/or decoration of the corrinoid ring (CobI operon functions) are absent aerobically. Cells can synthesize dimethyl benzimidazole and assemble B12 from cobinamide and dimethyl benzimidazole (CoblI and CoblII operon functions, respectively) under both aerobic and anaerobic conditions. Only four functions in S. typhimurium are known to require cobalamin (8,14,33,34,40; R. M. Jeter, submitted for publication).Escalante-Semerena and Roth (13) used Lac operon fusions to examine transcriptional regulation of the cobalamin biosynthetic genes. Their studies revealed that transcription of the cobinamide biosynthesis genes (CobI operon) is stimulated by cyclic AMP (cAMP) and that the end product (cobalamin or a derivative) signals repression. Furthermore, CobI transcription is strongly repressed in the presence of oxygen, suggesting the e...

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confidence: 99%

Redox regulation of the genes for cobinamide biosynthesis in Salmonella typhimurium

Andersson

Roth

1989

J Bacteriol

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“…Monophosphates and diphosphates of prenols were synthesized by phosphorylation of the corresponding prenols as described previously (17). Ubiquinone-8 and menaquinone-8 were isolated from E. coli W3110 as described previously (3).…”

Section: Methodsmentioning

confidence: 99%

Isolation and characterization of an Escherichia coli mutant having temperature-sensitive farnesyl diphosphate synthase

et al. 1989

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The screening of a collection of highly mutagenized strains of Escherichia coli for defects in isoprenoid synthesis led to the isolation of a mutant that had temperature-sensitive farnesyl diphosphate synthase. The defective gene, named ispA, was mapped at about min 10 on the E. coli chromosome, and the gene order was shown to be tsx-ispA-ion. The mutant ispA gene was transferred to the E. coli strain with a defined genetic background by P1 transduction for investigation of its function. The in vitro activity of farnesyl diphosphate synthase of the mutant was 21% of that of the wild-type strain at 30°C and 5% of that at 40°C. At 42°C the ubiquinone level was lower (66% of normal) in the mutant than in the wild-type strain, whereas at 30°C the level in the mutant was almost equal to that in the wild-type strain. The polyprenyl phosphate level was slightly higher in the mutant than in the wild-type strain at 30°C and almost the same in both strains at 42°C. The mutant had no obvious phenotype regarding its growth properties.It is well known that 3-hydroxy-3-methylglutaryl coenzyme A reductase is a rate-limiting enzyme in the biosyntheses of isoprenoid compounds, undergoing multivalentfeedback regulation (4). However, a branch point of the synthetic pathway of various isoprenoids seems to be a reaction utilizing isopentenyl diphosphate (IPP) or farnesyl diphosphate (FPP) or both. For elucidation of the mechanism by which the syntheses of various isoprenoids are regulated differently, many researchers have studied the regulation of activities of the enzymes, utilizing IPP or FPP or both as a substrate (1,(5)(6)(7)11).Escherichia coli includes isoprenoid quinones (ubiquinone-8, menaquinone-8, and demethylmenaquinone-8) having an all-E-octaprenyl side chain (8) and sugar carrier lipid (decaprenyl phosphate, undecaprenyl phosphate, and dodecaprenyl phosphate) containing a Z,E-mixed isoprenoid chain (27). Because the composition of isoprenoids in E. coli is simpler than that in eucaryotes, E. coli is a useful system as a model for studying the biosynthesis of nonsterol isoprenoids and its regulation. We have studied the biosynthetic enzymes, utilizing IPP as a substrate in E. coli, and separated IPP isomerase and three prenyltransferases, namely, FPP synthase, octaprenyl diphosphate synthase, and undecaprenyl diphosphate synthase, from each other (13). FPP synthase catalyzes the condensation of IPP with dimethylallyl diphosphate (C5) or geranyl diphosphate (C1O) to give FPP (C15). The latter two enzymes catalyze the sequential condensation of IPP with FPP to give long-chain polyprenyl diphosphates which are precursors of isoprenoid quinones and sugar carrier lipid.One effective approach to the elucidation of the role of a certain enzyme in vivo is to isolate the mutant containing the defective enzyme and to characterize it. We screened a collection of temperature-sensitive mutants of E. coli (24) for defects in isoprenoid synthesis by measuring 14C incorpora-* Corresponding author. Screening of temperature-sensitive mut...

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“…1969), afford an ideal means for studying menaquinone biosynthesis, since staphylococci, like the other Grampositive cocci, possess only one type of quinone (Bishop, Pandya & King, 1962;Jeffries et al 1967). The early stages of menaquinone biosynthesis are common to the biosynthesis of the aromatic amino acids (Cox & Gibson, 1964, 1966 up to the point of formation of chorismate or prephenate.…”

Section: Introductionmentioning

confidence: 99%