A radical-chemical route to acetyl-CoA: the anaerobically induced pyruvate formate-lyase system of Escherichia coli

Knappe, J

doi:10.1016/0378-1097(90)90689-n

Cited by 99 publications

(147 citation statements)

References 49 publications

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“…Although this behavior did exist in the unregulated modeled population as a relatively small set of cells at intermediate to fast growth rates, the number of cells predicted to engage in this behavior is significantly expanded under regulation due to the lack of alternate avenues for NADH oxidation. Interestingly, both PFL and LDH use are known to be associated with anaerobic growth (28,29). The microarray data used in imposing regulatory constraints indicates that PFL is downregulated a modest 2.6-fold-well below our cutoff for strong down-regulation-despite an average measured copy number in excess of 200 per cell.…”

Section: Growth Rates and Flux Distributionsmentioning

confidence: 99%

Heterogeneity in protein expression induces metabolic variability in a modeled Escherichia coli population

Labhsetwar

Cole²,

Roberts

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

117

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The authors note, "For the 'hybrid' location discrimination task, we report data obtained from 27 electrodes, 16 of which were in area 1; the 11 electrodes in area 3b were divided evenly across the two animals (6 and 5). We had previously tested all of the electrodes, including those in area 3b, in the detection and discrimination tasks (as shown in Fig. 3) and found them all to yield approximately equivalent performance (see Fig 3A). We noticed in the hybrid location discrimination task, however, that one of the animals performed much more poorly based on stimulation of area 3b than it did based on stimulation of area 1 (while the other animal performed better based on stimulation of area 1). Having no reason to question any of the arrays, we attributed this discrepancy to differences across animals and arrived at the conclusion, based on pooled data from both animals, that stimulation of the two areas yields equivalent performance in the 'hybrid location discrimination' task. The overall conclusion, then, was that stimulation of neurons in area 3b and 1 evokes percepts that are equally localized on the skin."Shortly after publication of the paper, we repeated detection experiments across the arrays and found that the animal could no longer detect stimulation through the array in area 3b that had yielded poor performance in the hybrid location discrimination task. It is therefore likely that this array had failed between the time we conducted the initial detection and discrimination experiments and the time we conducted the hybrid location discrimination task (which required 2-3 months of retraining). If this is the case, and we eliminate data from that bad array, then the median performance on hybrid trials is 83% (up from the 80% that was originally reported), which is still statistically poorer than that on the location-matched mechanical trials [median difference between performance on mechanical and hybrid trials was 3.3% rather than 5.6%, t (119) = 6.1, P < 0.001] (see the corrected Fig. 2). Thus, we probably underestimated overall performance on hybrid trials, and thus the degree to which artificial percepts are localized, in the original publication. Importantly, however, performance on hybrid trials based on stimulation of area 3b was significantly better than performance based on stimulation of area 1 [median Δp = 0.028 and 0.054 for areas 3b and 1, respectively; t test: t (76) = 2.8, P < 0.01]. Thus, based on the data obtained from only one animal, it seems as though stimulation of area 3b elicits more localized percepts than does stimulation of area 1, as might be expected given that neurons in area 3b tend to have smaller receptive fields than their counterparts in area 1 (1, 2)."As a result of this error, Fig. 2 and its legend appeared incorrectly. The corrected figure and its corresponding legend appear below. On both mechanical and hybrid trials, the relative locations of stimuli applied to widely spaced digits were more accurately discriminated than were the relative locations of stimuli applie...

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Section: Growth Rates and Flux Distributionsmentioning

confidence: 99%

Heterogeneity in protein expression induces metabolic variability in a modeled Escherichia coli population

Labhsetwar

Cole²,

Roberts

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

117

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“…Such flickering was found in other ion channels, including the inward-rectifying potassium channel Kir2.1 (23) and also the ClC chloride channels (24,25). The "fast gate" could be a single, flexible amino acid side chain in the transport channel, as is the case with the "Glu ex " glutamate residue in ClC channels (25,26). Its strict conservation within the FNT family makes H209 in the center of the channel a likely candidate (Fig.…”

Section: Discussionmentioning

confidence: 93%

The formate channel FocA exports the products of mixed-acid fermentation

Lü

Schwarzer

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Formate is a major metabolite in the anaerobic fermentation of glucose by many enterobacteria. It is translocated across cellular membranes by the pentameric ion channel/transporter FocA that, together with the nitrite channel NirC, forms the formate/nitrite transporter (FNT) family of membrane transport proteins. Here we have carried out an electrophysiological analysis of FocA from Salmonella typhimurium to characterize the channel properties and assess its specificity toward formate and other possible permeating ions. Single-channel currents for formate, hypophosphite and nitrite revealed two mechanistically distinct modes of gating that reflect different types of structural rearrangements in the transport channel of each FocA protomer. Moreover, FocA did not conduct cations or divalent anions, but the chloride anion was identified as further transported species, along with acetate, lactate and pyruvate. Formate, acetate and lactate are major end products of anaerobic mixed-acid fermentation, the pathway where FocA is predominantly required, so that this channel is ideally adapted to act as a multifunctional export protein to prevent their intracellular accumulation. Because of the high degree of conservation in the residues forming the transport channel among FNT family members, the flexibility in conducting multiple molecules is most likely a general feature of these proteins.electrophysiology | planar lipid bilayer | formate channel

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“…Western blot analysis of the levels of pyruvate formate-lyase (PflB), which generates formate from the cleavage of pyruvate (Knappe & Sawers, 1990), revealed that PflB levels (Fig. 3a, bottom panel) correlated with the presence of the Hyd-3 large subunit (Fig.…”

Section: Manno(fructo)kinase Is Not the Main Route Of Fructose Entry mentioning

confidence: 99%

“…3a). The double band in the Western blot of PflB is indicative of the presence of active, radicalcontaining enzyme in the cell at the time of cell breakage (Knappe & Sawers, 1990). …”

Section: Manno(fructo)kinase Is Not the Main Route Of Fructose Entry mentioning

confidence: 99%

Analysis of hydrogenase 1 levels reveals an intimate link between carbon and hydrogen metabolism in Escherichia coli K-12

et al. 2012

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Two of the three [NiFe]-hydrogenases (Hyd) of Escherichia coli have a hydrogen-uptake function in anaerobic metabolism. While Hyd-2 is maximally synthesized when the bacterium grows by fumarate respiration, Hyd-1 synthesis shows a correlation with fermentation of sugar substrates. In an attempt to advance our knowledge on the physiological function of Hyd-1 during fermentative growth, we examined Hyd-1 activity and levels in various derivatives of E. coli K-12 MC4100 with specific defects in sugar utilization. MC4100 lacks a functional fructose phosphotransferase system (PTS) and therefore grows more slowly under anaerobic conditions in rich medium in the presence of D-fructose compared with D-glucose. Growth in the presence of fructose resulted in an approximately 10-fold increase in Hyd-1 levels in comparison with growth under the same conditions with glucose. This increase in the amount of Hyd-1 was not due to regulation at the transcriptional level. Reintroduction of a functional fruBKA-encoded fructose PTS into MC4100 restored growth on D-fructose and reduced Hyd-1 levels to those observed after growth on D-glucose. Reducing the rate of glucose uptake by introducing a mutation in the gene encoding the cAMP receptor protein, or consumption through glycolysis, by introducing a mutation in phosphoglucose isomerase, increased Hyd-1 levels during growth on glucose. These results suggest that the ability to oxidize hydrogen by Hyd-1 shows a strong correlation with the rate of carbon flow through glycolysis and provides a direct link between hydrogen, carbon and energy metabolism.

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A radical-chemical route to acetyl-CoA: the anaerobically induced pyruvate formate-lyase system of Escherichia coli

Cited by 99 publications

References 49 publications

Heterogeneity in protein expression induces metabolic variability in a modeled Escherichia coli population

Heterogeneity in protein expression induces metabolic variability in a modeled Escherichia coli population

The formate channel FocA exports the products of mixed-acid fermentation

Analysis of hydrogenase 1 levels reveals an intimate link between carbon and hydrogen metabolism in Escherichia coli K-12

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