Lipoquinones of Escherichia coli

Polglase, W. J.; Pun, Wing; Withaar, J.

doi:10.1016/s0926-6593(66)80053-x

Cited by 49 publications

(21 citation statements)

References 4 publications

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“…It was reported earlier for E. coli that Q is preferentially formed in bacteria grown under aerobic and MK under anaerobic conditions [34]. However, no conclusions were drawn on the particular roles of the two quinones.…”

Section: Growth Conditionsmentioning

confidence: 93%

On the Role of Quinones in Bacterial Electron Transport

Kröger¹,

Dadák

Klingenberg³

et al. 1971

European Journal of Biochemistry

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The individual roles of ubiquinone and menaquinone in the electron transport of Proteus rettgeri have been investigated and their functional positions with respect to the cytochromes and dehydrogenases elucidated.1. A method has been developed for the parallel determination of both ubiquinone and menaquinone in the nanomole range in the same extract.2. Ubiquinone and menaquinone are not separated by various methods of cell disintegration and remain associated with the cytochromes.3. The relative contents of ubiquinone and menaquinone are independent of the hydrogen source and depend on the redox acceptor offered in the growth medium. As in Escherichia coli, ubiquinone is preferentially formed in cutures with maximal oxygen supply and menaquinone in anaerobic cultures. The activity offurnarate reduction by NADH and by formate parallels the content of menaquinone. 4.On extraction of the quinones the electron transport is inhibited. Ubiquinone reactivates the respiration with succinate, NADH and formate and menaquinone restores the fumarate reduction. I n anaerobically grown P . rettgeri the respiration with NADH and formate is partly restored by menaquinone, too.5. In the anaerobic states, ubiquinone is reduced with succinate, NADH and formate, and menaquinone with NADH and formate only. Ubiquinone is partly oxidized in the steady state of respiration and completely reduced in the steady state of fumarate reduction, where menaquinone is partly oxidized.6. 2-n-Heptyl-4-hydroxyquinoline-N-oxide inhibits the respiration of succinate, NADH and formate a t a common site located on the oxygen side of ubiquinone.7. Two b-type cytochromes (besides cytochrome 0) are differentialed: (1) Cytochrome b B is situated on the substrate side of 2-n-heptyl-4-hydroxyquinoline-N-oxide action and is reduced by formate only. (2) Cytochrome b1 is located on the oxygen side of this action and is reducible by all substrates.I n a previous communication [l] the role of the naphthoquinone derivative, menaquinone, was studied in a gram-positive organism (Bacillus megaterium) where it is the only occurring quinone. A basically similar role in the electron transport was attributed to menaquinone (MK) as to ubiquinone (Q) in mitochondria. A more penetrating insight into the particular role of both quinones and their differences is expected to be gained from the study of an organism where both quinones occur together, such as in the entero-bacteria, Escherichia and Proteus [2,3]. Different roles for Q and MK can be expected from the considerable differences or their redox potentials (see Discussion).Unusual Abbreviations. Ubiquinone, Q ; oxidized ubiquinone, Qox ; reduced ubiquinone, Qred ; menaquinone (vitamin K2), MK; oxidized menaquinone, MK,,; reduced menaquinone, =red.It is generally assumed that both quinones interact in the electron transport system of these organisms [4-91 although no redox reactions of MK have been demonstrated so far. Furthermore, the individual roles as reported in the literature have not been understood so far [lo-12...

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Section: Growth Conditionsmentioning

confidence: 93%

On the Role of Quinones in Bacterial Electron Transport

Kröger¹,

Dadák

Klingenberg³

et al. 1971

European Journal of Biochemistry

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“…These comprise UQ-8 and MQ-8 and predominate under oxidizing and reducing conditions, respectively. 12,[29][30][31] NarGHI is able to bind and oxidize both major quinol species at its Q-site. 32,33 Given that the heme b D heterogeneity appears to decrease with decreasing aeration during cell growth and is not eliminated in the absence of cardiolipin we speculated that it may be related to the composition of quinones within the E. coli cytoplasmic membrane.…”

Section: Influence Of Q-site Structure and Occupancy On Heme B D Epr mentioning

confidence: 99%

Q-Site Occupancy Defines Heme Heterogeneity in Escherichia coli Nitrate Reductase A (NarGHI)

et al. 2014

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The membrane subunit (NarI) of Escherichia coli nitrate reductase A (NarGHI) contains two btype hemes, both of which are the highly anisotropic low-spin type. Heme b D is distal to NarGH and constitutes part of the quinone binding and oxidation site (Q-site) through the axially coordinating histidine-66 residue and one of the heme b D propionate groups. Bound quinone participates in hydrogen bonds with both the imidazole of His66 and the heme propionate, rendering the EPR spectrum of the heme b D sensitive to Q-site occupancy. As such, we hypothesize that the heterogeneity in the heme b D EPR signal arises from the differential occupancy of the Q-site. In agreement with this, the heterogeneity is dependent upon growth conditions but is still apparent when NarGHI is expressed in a strain lacking cardiolipin. Furthermore, this heterogeneity is sensitive to Q-site variants, NarI-G65A and NarI-K86A, and is collapsible by the binding of inhibitors. We found that the two main g z components of heme b D exhibit differences in reduction potential and pH dependence, which we posit is due to differential Q-site occupancy. Specifically, in a quinone-bound state, heme b D exhibits an E m,8 of −35 mV and a pH dependence of −40 mV pH −1 . In the quinone-free state, however, heme b D titrates with an E m,8 of +25 mV and a pH dependence of −59 mV pH −1 . We hypothesize that quinone binding modulates the electrochemical properties of heme b D as well as its EPR properties.Nitrate reductase A (NarGHI) from Escherichia coli is a membrane-bound quinol:nitrate oxidoreductase that is expressed under anaerobic conditions in the presence of nitrate. 1 It The authors declare no competing financial interest. Supporting InformationResults of the cytochrome bd and bo 3 deletions on NarGHI EPR heme spectra as well as anaerobic growth curves for NarGHI, NarGHI-K86A, NarGHI-G65A, and the background strain, LCB79. This material is available free of charge via the Internet at http:// pubs.acs.org. CIHR Author Manuscript CIHR Author Manuscript CIHR Author Manuscriptfunctions as a terminal reductase, coupling quinol oxidation to nitrate reduction, and contributes to the generation of a proton electrochemical potential across the cytoplasmic membrane. 2 NarGHI comprises a catalytic subunit (NarG, 140 kDa), an electron-transfer subunit (NarH, 58 kDa), and a membrane anchor subunit (NarI, 26 kDa). NarG contains a molybdo-bis(pyranopterin guanine dinucleotide) (Mo-bisPGD) cofactor that is the site of nitrate reduction as well as a single tetranuclear iron-sulfur ([4Fe-4S]) cluster known as FS0. NarH contains three [4Fe-4S] clusters (FS1-FS3) and one trinuclear iron-sulfur cluster ([3Fe-4S], FS4). NarI anchors the NarGH subunits to the inside of the cytoplasmic membrane and contains two hemes b that are proximal (b P ) and distal (b D ) to the NarGH subunits, respectively. Overall, these subunits provide a molecular scaffold for an electrontransfer relay connecting the site of quinol oxidation adjacent to heme b D in NarI (the Qsite) with the...

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“…The naphthoquinone level is significantly up-regulated during the aerobiosis-to-anaerobiosis transition (15)(16)(17), indicating that menaquinone biosynthesis is subject to aeration control. However, the O 2 -dependent Arc, Fnr, and AppY transcriptional regulatory systems have been demonstrated not to regulate the biosynthesis of menaquinone by gene knock-out experiments (18,19).…”

mentioning

confidence: 99%

A Bicarbonate Cofactor Modulates 1,4-Dihydroxy-2-naphthoyl-Coenzyme A Synthase in Menaquinone Biosynthesis of Escherichia coli

Jiang

Chen

Guo

et al. 2010

Journal of Biological Chemistry

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1,4-Dihydroxy-2-naphthoyl coenzyme A (DHNA-CoA) synthase is a typical crotonase-fold protein catalyzing an intramolecular Claisen condensation in the menaquinone biosynthetic pathway. We have characterized this enzyme from Escherichia coli and found that it is activated by bicarbonate in a concentration-dependent manner. The bicarbonate binding site has been identified in the crystal structure of a virtually identical ortholog (96.8% sequence identity) from Salmonella typhimurium through comparison with a bicarbonate-insensitive orthologue. Kinetic properties of the enzyme and its site-directed mutants of the bicarbonate binding site indicate that the exogenous bicarbonate anion is essential to the enzyme activity. With this essential catalytic role, the simple bicarbonate anion is an enzyme cofactor, which is usually a small organic molecule derived from vitamins, a metal ion, or a metal-containing polyatomic anionic complex. This finding leads to classification of the DHNA-CoA synthases into two evolutionarily conserved subfamilies: type I enzymes that are bicarbonate-dependent and contain a conserved glycine at the bicarbonate binding site; and type II enzymes that are bicarbonate-independent and contain a conserved aspartate at the position similar to the enzyme-bound bicarbonate. In addition, the unique location of the enzymebound bicarbonate allows it to be proposed as a catalytic base responsible for abstraction of the ␣-proton of the thioester substrate in the enzymatic reaction, suggesting a unified catalytic mechanism for all DHNA-CoA synthases.Menaquinone is a lipid soluble naphthoquinone that plays important biological roles. In many bacterial microorganisms, menaquinone serves as an electron transporter in the respiratory chain and is essential for their survival (1, 2). In humans and animals, menaquinone is a vitamin (K2) and is used as an enzyme cofactor involved in post-translational glutamate ␥-carboxylation of proteins in blood coagulation (3, 4), bone metabolism (5), and calcification of arteries and other soft tissues (6). This naphthoquinone is synthesized from the chorismate of the shikimate pathway in microorganisms (1, 2, 7, 8), whereas it has to be acquired from diet or intestinal microflora in humans or animals (9, 10). Due to its absence in humans and animals, menaquinone biosynthesis has been an attractive target for development of antibiotics against a number of important microbial pathogens, such as Mycobacterium tuberculosis and Staphylococcus aureus (11,12).Menaquinone biosynthesis has been most extensively studied in the facultative anaerobe Escherichia coli that uses the naphthoquinone (MK-8) and its demethylated congener (demethylmenaquinone, DMK-8) as an obligatory electron transporter under anaerobic conditions when the electron acceptor is fumarate, dimethyl sulfoxide, or trimethylamine N-oxide (13,14). The naphthoquinone level is significantly up-regulated during the aerobiosis-to-anaerobiosis transition (15-17), indicating that menaquinone biosynthesis is subject to aerati...

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Lipoquinones of Escherichia coli

Cited by 49 publications

References 4 publications

On the Role of Quinones in Bacterial Electron Transport

On the Role of Quinones in Bacterial Electron Transport

Q-Site Occupancy Defines Heme Heterogeneity in Escherichia coli Nitrate Reductase A (NarGHI)

A Bicarbonate Cofactor Modulates 1,4-Dihydroxy-2-naphthoyl-Coenzyme A Synthase in Menaquinone Biosynthesis of Escherichia coli

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