The relationship between intracellular pH, the pH gradient and potassium transport in <i>Escherichia coli</i>

Kroll, R.G.; Booth, Ian R.

doi:10.1042/bj2160709

Cited by 95 publications

(73 citation statements)

References 27 publications

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“…(a) increase of the internal pH by K + uptake and (b) the necessity of high internal K + concentrations for effective function of the glutamate uptake system. K+-depleted cells show relatively poor internal pH homeostasis, as already reviewed in general for E. coli and other organisms [20,23,24]. We found that at external pH values below 7.5 the internal pH was always definitely lower than the external value in K+-depleted cells.…”

Section: Discussionsupporting

confidence: 50%

Uptake of glutamate in Corynebacterium glutamicum

Krämer

Lambert

Hoischen

et al. 1990

European Journal of Biochemistry

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The active uptake system for glutamate in Corynebacterium glutamicum is inducible by growth on glutamate as sole energy and carbon source and is also susceptible to catabolite repression by glucose. The basic level of uptake activity is low in glucose‐grown cells (1.5 nmol · mg dry mass−1· min−1), it is intermediate when acetate is the carbon source (3.8 nmol · mg dry mass−1· min−1) and becomes fully induced by glutamate (15 nmol · mg dry mass−1· min−1). In all cases the uptake has, except for different Vmax values, identical kinetic and energetic properties, and is characterized by a low apparent Km value of 0.5–1.3 μM and by high substrate specificity. The transported substrate species is the deprotonated form which can also be concluded from the extremely high pH optimum of transport above pH 9. Glutamate uptake in cells grown in media with low K+ concentration is not influenced by external Na+ but is drastically stimulated by addition of K+. Stimulation by K+ could be separated into two different mechanisms. (a) Addition of K+ increases the internal pH, thereby stimulating glutamate uptake which is regulated by the internal pH in C. glutamicum. The apparent pK of the internal ‘pH switch’ is 6.6; below this value, uptake of glutamate is inhibited. (b) Internal K+ also directly promotes glutamate uptake. Effective uptake of glutamate can be observed only when the cytosolic K+ concentration exceeds a threshold value of about 200 mM. Stimulation of glutamate uptake by external K+ is not due to functional coupling of K+ and glutamate transport but reveals the necessity to replenish the internal K+ pool.

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Section: Discussionsupporting

confidence: 50%

Uptake of glutamate in Corynebacterium glutamicum

Krämer

Lambert

Hoischen

et al. 1990

European Journal of Biochemistry

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“…Previously, the Na + \H + and K + \H + antiports, H + pumps and active K + transport have been proposed as being part of the pH homeostatic system in bacteria (Padan et al, 1981 ;Kroll & Booth, 1983 ;Booth, 1985 ;Nakamura et al, 1984 ;Krulwich, 1995), but as suggested by Padan & Schuldiner (1987), there might be other systems (ions or leaks of Na + and K + ) that form part of the regulatory system. We propose that Ca# + transport systems might play a direct role in pHi regulation at low external pH values, acting to increase the cytoplasmic pH.…”

Section: mentioning

confidence: 99%

“…Two mechanisms are thought to be primarily involved in homeostasis of intracellular pH (pHi), one to raise and another to lower the cytoplasmic pH. Studies involving a range of organisms have identified active K + uptake as a major means of regulating pHi when the external pH (pHex) is acidic (Kroll & Booth, 1983 ;Nakamura et al, 1992), and both Na + \H + and K + \H + antiporters are thought to be involved in the regulation of pHi when the external pH is alkaline (Kroll & Booth, 1983 ;Padan & Schuldiner, 1987 ;Krulwich, 1995). In both cases, the movement of monovalent cations, *Author for correspondence (tel j3491 397 8176 ; fax j3491 397 8344 ; e-mail Francisca.Pina!uam.es).…”

Section: mentioning

confidence: 99%

Role of external calcium in homeostasis of intracellular pH in the cyanobacterium Anabaena sp. strain PCC7120 exposed to low pH

1999

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The role of external Ca2+ in the homeostasis of intracellular pH (pHi) of Anabaena sp. strain PCC7120 in response to a decrease in the external pH (pHex) has been studied in cell suspensions. Increase in cytoplasmic pH after acid shock is dependent on the presence of Ca2+ in the medium. The observed Ca2+‐mediated alkalization of the cytoplasm depends on the extent of the shift in external pH. Acid pH shifts resulted in an increased permeability of the cytoplasmic membrane to protons, which could be reversed by increasing the concentration of Ca2+ in the medium. Thus, the ability of Ca2+ to increase cytoplasmic pH might be correlated with an inhibition of net proton uptake by increasing concentrations of external Ca2+ under these conditions. This combined response resulted in the generation and maintenance of a larger pH gradient (ΔpH) at acid external pH values. All Ca2+ channel blockers tested, such as verapamil and LaCl3, inhibited the observed Ca2+‐mediated response. On the other hand, the Ca ionophore calcimycin (compound A23187) was agonistic, and stimulated both cytoplasmic alkalization and inhibition of net proton uptake. The protonophorous uncoupler carbonylcyanide m‐chlorophenyl hydrazone, inhibited this Ca2+‐mediated response, whereas monensin, an inhibitor of the Na+/H+ antiporter, had no significant effect. The results of the present study suggest that an influx of Ca2+ from the extracellular space is required for the regulation of cytoplasmic pH in Anabaena sp. strain PCC7120 exposed to low external pH values.

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“…or the leading-twist generation of the meson underestimates the handbag contribution [35]. However, by forming the π − /π + ratio the nonperturbative components represented by the form factors and meson distribution amplitude may be divided out, allowing the perturbative contribution to be observed more readily.…”

Section: Resultsmentioning

confidence: 99%

“…However, by forming the π − /π + ratio the nonperturbative components represented by the form factors and meson distribution amplitude may be divided out, allowing the perturbative contribution to be observed more readily. In the limit that the soft contributions are completely divided out, the one-hard-gluon-exchange calculation predicts [35] the simple scaling behavior…”

Section: Resultsmentioning

confidence: 99%

Separated response functions in exclusive, forwardπ±electroproduction on deuterium

Huber¹,

Blok²,

Butuceanu³

et al. 2015

Phys. Rev. C

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Background: Measurements of forward exclusive meson production at different squared four-momenta of the exchanged virtual photon, Q 2 , and at different four-momentum transfer, t, can be used to probe QCD's transition from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales. Ratios of separated response functions in π − and π + electroproduction are particularly informative. The ratio for transverse photons may allow this transition to be more easily observed, while the ratio for longitudinal photons provides a crucial verification of the assumed pole dominance, needed for reliable extraction of the pion form factor from electroproduction data.Purpose: Perform the first complete separation of the four unpolarized electromagnetic structure functions L/T /LT /T T in forward, exclusive π ± electroproduction on deuterium above the dominant resonances.Method: Data were acquired with 2.6-5.2 GeV electron beams and the HMS+SOS spectrometers in Jefferson Lab Hall C, at central Q 2 values of 0.6, 1.0, 1.6 GeV 2 at W =1.95 GeV, and Q 2 = 2.45 GeV 2 at W =2.22 GeV. There was significant coverage in φ and ǫ, which allowed separation of σL,T,LT,T T . 2Results: σL shows a clear signature of the pion pole, with a sharp rise at small −t. In contrast, σT is much flatter versus t. The longitudinal/transverse ratios evolve with Q 2 and t, and at the highest Q 2 = 2.45 GeV 2 show a slight enhancement for π − production compared to π + . The π − /π + ratio for transverse photons exhibits only a small Q 2 -dependence, following a nearly universal curve with t, with a steep transition to a value of about 0.25, consistent with s-channel quark knockout. The σT T /σT ratio also drops rapidly with Q 2 , qualitatively consistent with s-channel helicity conservation. The π − /π + ratio for longitudinal photons indicates a small isoscalar contamination at W =1.95 GeV, consistent with what was observed in our earlier determination of the pion form factor at these kinematics. Conclusions: The separated cross sections are compared to a variety of theoretical models, which generally describe σL but have varying success with σT . Further theoretical input is required to provide a more profound insight into the relevant reaction mechanisms for longitudinal and transverse photons, such as whether the observed transverse ratio is indeed due to a transition from pion to quark knockout mechanisms, and provide useful information regarding the twist-3 transversity generalized parton distribution, HT .

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The relationship between intracellular pH, the pH gradient and potassium transport in Escherichia coli

Cited by 95 publications

References 27 publications

Uptake of glutamate in Corynebacterium glutamicum

Uptake of glutamate in Corynebacterium glutamicum

Role of external calcium in homeostasis of intracellular pH in the cyanobacterium Anabaena sp. strain PCC7120 exposed to low pH

Separated response functions in exclusive, forwardπ±electroproduction on deuterium

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