Search PubMed⌕ Search

Biomedical subjects

S Engelbrecht

Publications and source records attributed to S Engelbrecht.

At least 55 records · Page 3Linked to original sources
PubMed1994

Over-production, renaturation and reconstitution of delta and epsilon subunits from chloroplast and cyanobacterial F1.

We studied the functioning of chimeric F0F1-ATPases by replacing subunits delta and epsilon of spinach CF1 with their counterparts from Synechocystis sp. PCC 6803. The sequence identities between these subunits are 26 and 41%, respectively. For a systematic approach to such studies and later extension to genetically modified subunits recombinant proteins are required. The genes coding for spinach and Synechocystis delta and epsilon were cloned into pET3 expression vectors and expressed in Escherichia coli. Upon expression at 37 degrees C the recombinant subunits formed inclusion bodies within the host cells except for spinach delta, which was soluble. Synechocystis delta and epsilon could be obtained in soluble form upon expression at 20 degrees C. After purification (and refolding of spinach epsilon) both epsilon subunits inhibited the Ca(2+)-ATPase activity of soluble CF1(- epsilon). Subunits delta and epsilon from both species raised the rate of ATP synthesis in partially CF1-depleted spinach thylakoids when added together with CF1(- delta) or CF1(- delta, epsilon). This showed the functionality of recombinant Synechocystis and spinach delta and epsilon together with spinach alpha 3 beta 3 gamma. The molar excess of epsilon necessary for saturation was higher for Ca(2+)-ATPase inhibition than for reconstitution of photophosphorylation thus pointing to a direct interaction between epsilon and both CF1 and CF0.

Amino Acid Sequence↗
PubMed1994

Complementation of Escherichia coli uncD mutant strains by a chimeric F1-beta subunit constructed from E. coli and spinach chloroplast F1-beta.

ATP-synthesizing F0F1-ATPases are complex enzymes consisting of at least eight different subunits. These subunits are conserved during evolution to a very variable degree ranging in pairwise comparison between, for example, Escherichia coli and spinach chloroplast from 20% to 66% identical residues. It was surprising to find that some of the less well conserved subunits like delta and epsilon could replace their E. coli counterparts, whereas the highly conserved beta subunit, which carries the active site, in the E. coli enzyme could not be substituted by spinach chloroplast beta (Lill et al. (1993) Biochim. Biophys. Acta 1144, 278-284). We constructed a chimeric F1-beta subunit consisting of spinach beta in which the 96 N-terminal amino acids were replaced by the respective residue sequence from E. coli beta. Whereas spinach beta did not complement E. coli uncD mutant strains, the chimeric beta subunit restored growth under conditions of oxidative phosphorylation.

Amino Acid Sequence↗
PubMed1994

Evaluation of commercially available assays for antibodies to HIV-1 in serum obtained from South African patients infected with HIV-1 subtypes B, C, and D.

Between 1984 and 1990, virus was routinely isolated and serum collected from patients diagnosed at hospitals in the Western Cape as suffering from AIDS or AIDS-related conditions (ARC). From these, 17 virus strains were selected at random for sequencing and molecular characterisation of the env gene. The strains were previously characterised as belonging to HIV-1 subtypes B, C and D. The purpose of the present study was to evaluate retrospectively the serological diagnosis of HIV-1 in these 17 South African patients. Thirteen anti-HIV screening assays, including 7 rapid/simple test devices (RTDs), 4 enzyme-linked immunosorbent assays (EIAs) and 2 Western immunoblot assays were evaluated. Using commercial EIAs, 16 serum samples were HIV antibody-positive and these results were confirmed by Western immunoblot analysis. Serum from one terminal AIDS patient was found negative with all the serological tests. Some RTDs gave false negative antibody reactions on specimens from patients infected with subtype D strains. To investigate the false negative antibody reactions, the polymerase chain reaction (PCR) was used to amplify, clone and sequence proviral DNA from the immunodominant gp41 region from 7 of the HIV-1 strains. Two patients, both subtype D strains (D214 and D482) with false negative results in the RTDs, showed a significant amino acid substitution, i.e., substitution of a histidine residue for leucine at env position 607. It was concluded that although there were false negative RTD reactions on patients with HIV-1 subtype D strains, the commercial EIAs tested are sensitive and are able to detect patients infected with HIV-1 subtypes B, C and D that are present in South Africa.

AIDS-Related Complex↗
PubMed1993

Complementation of Escherichia coli unc mutant strains by chloroplast and cyanobacterial F1-ATPase subunits.

The genes encoding the five subunits of the F1 portion of the ATPases from both spinach chloroplasts and the cyanobacterium Synechocystis sp. PCC 6803 were cloned into expression vectors and expressed in Escherichia coli. The recombinant subunits formed inclusion bodies within the cells. Each particular subunit was expressed in the respective unc mutant, each unable to grow on non-fermentable carbon sources. The following subunits restored growth under conditions of oxidative phosphorylation: alpha (both sources, cyanobacterial subunit more than spinach subunit), beta (cyanobacterial subunit only), delta (both spinach and Synechocystis), and epsilon (both sources), whereas no growth was achieved with the gamma subunits from both sources. Despite a high degree of sequence homology the large subunits alpha and beta of spinach and cyanobacterial F1 were not as effective in the substitution of their E. coli counterparts. On the other hand, the two smallest subunits of the E. coli ATPase could be more effectively replaced by their cyanobacterial or chloroplast counterparts, although the sequence identity or even similarity is very low. We attribute these findings to the different roles of these subunits in F1: The large alpha and beta subunits contribute to the catalytic centers of the enzyme, a function rendering them very sensitive to even minor changes. For the smaller delta and epsilon subunits it was sufficient to maintain a certain tertiary structure during evolution, with little emphasis on the conservation of particular amino acids.

Amino Acid Sequence↗
PubMed1992

Added subunit beta of CF1 as well as gamma/delta/epsilon restore photophosphorylation in partially CF1-depleted thylakoids.

We investigated the ability of subunits beta, gamma, delta, and epsilon of CF1, the F1-ATPase of chloroplasts, to interact with exposed CF0 in EDTA-treated, partially CF1-depleted thylakoid membranes. We measured the ability of subunits beta, gamma, delta, and epsilon to stimulate the rate of photophosphorylation under continuous light and, for subunit beta, also the ability to diminish the proton leakage through exposed CF0 by deceleration of the decay of electrochromic absorption transients under flashing light. The greatest effect was caused by subunit beta, followed by gamma/delta/epsilon. Pairwise combinations of gamma, delta, and epsilon or each of these subunits alone were only marginally effective. Subunit gamma from the thermophilic bacterium PS 3 in combination with chloroplast delta and epsilon was as effective as chloroplast gamma. The finding that the small CF1 subunits in concert and the beta subunit by itself specifically interacted with the exposed proton channel CF0, qualifies the previous concept of subunit delta acting particularly as a plug to the open CF0 channel. The interactions between the channel and the catalytic portion of the enzyme seem to involve most of the small, and at least beta of the large subunits.

Amino Acid Sequence↗
PubMed1992

THE CHLOROPLAST H+-ATPase: PARTIAL REACTIONS OF THE PROTON.

This article reviews proton intake, charge transfer and proton release by F-ATPases, based in part on flash spectrophotometric studies on the chloroplast ATPase in thylakoid membranes, CF1Fo. The synthesis-coupled translocation of charges by CF1Fo (maximum rate <1500 s-1) and the dissipative flow through its exposed channel portion, CFo (rate >10 000 s-1), are extremely proton-specific (selectivity H+:K+>10(7):1). The proton-specific filter is located in CFo. Proton flow through exposed CFo can be throttled by adding subunit (&dgr;) or subunit &bgr; of CF1. These subunits thus may provide energy-transducing contacts between CF1 and CFo. Recently, we characterized two conditions where, in contrast to the above situation, proton intake by CF1Fo was decoupled from proton transfer across the main dielectric barrier: (a) CF1Fo structurally distorted by low ionic strength transiently trapped protons in a highly cooperative manner, but remained proton tight. This result has been interpreted in terms of Mitchell's proton well. (b) In the absence of nucleotides there is a proton slip. Addition of nucleotides (100 nmol l-1 ADP) abolished proton conduction but not proton intake by CF1Fo. These experiments functionally tag proton binding groups on CF1Fo that are located before the main dielectric barrier.

Journal Article↗
PubMed1990

Reconstitution of photophosphorylation in EDTA-treated thylakoids by added chloroplast coupling factor 1 (ATPase) and chloroplast coupling factor 1 lacking the delta subunit. Structural or functional?

Upon EDTA treatment thylakoids lose the chloroplast coupling factor 1 (CF1) part of their ATP synthase, CF0CF1, this exposes the proton channel, CF0. The previously established ability of the CF1 subunit delta to block the proton leak through CF0 prompted us to study (a) the ability of complete CF1 and, for comparison, CF1 lacking the delta subunit to block proton leakage and thereby to reconstitute structurally some photophosphorylation activity of the remaining CF0CF1 molecules and (b) their ability to form functional enzymes (functional reconstitution). In order to discriminate between activities caused by added CF1 or CF1(-delta) and remaining CF0CF1, the former were inhibited by chemical modification of subunit beta by N,N'-dicyclohexyl carbodiimide (DCCD) and the latter by tentoxin. We found that added CF1 acted both structurally and functionally while added DCCD-treated CF1 (DCCD-CF1) acted only structurally. In contrast to previous observations, CF1(-delta) and DCCD-CF1(-delta) also acted structurally although the reduction of proton leakage was smaller than with DCCD-CF1. Hence there was no functional reconstitution without subunit delta present. Previous studies indicated that only a small fraction of exposed CF0 is highly conducting and that this small fraction is distinguished by its high affinity for added CF1. The results of this study point rather to a wider distribution of CF0 conductance states and binding affinities.

Cell-Free System↗
PubMed1990

Subunit delta of H(+)-ATPases: at the interface between proton flow and ATP synthesis.

The ATP synthases in photophosphorylation and respiration are of the F-type with a membrane-bound proton channel, F0, and an extrinsic catalytic portion, F1. The properties of one particular subunit, delta (in chloroplasts and Escherichia coli) and OSCP (in mitochondria), are reviewed and the role of this subunit at the interface between F0 and F1 is discussed. Delta and OSCP from the three sources have in common the molecular mass (approximately 20 kDa), an elongated shape (axial ratio in solution about 3:1), one high-affinity binding site to F1 (Kd approximately 100 nM) plus probably one or two further low-affinity sites. When isolated delta is added to CF1-depleted thylakoid membranes, it can block proton flow through exposed CF0 channels, as do CF1 or CF1(-delta)+ delta. This identifies delta as part of the proton conductor or, alternatively, conformational energy transducer between F0 (proton flow) and F1 (ATP). Hybrid constructs as CF1(-delta)+ E. coli delta and EF1(-delta)+ chloroplast delta diminish proton flow through CF0.CF1(-delta) + E. coli delta does the same on EF0. Impairment of proton leaks either through CF0 or through EF0 causes "structural reconstitution' of ATP synthesis by remaining intact F0F1. Functional reconstitution (ATP synthesis by fully reconstructed F0F1), however, is absolutely dependent on the presence of subunit delta and is therefore observed only with CF1 or CF1(-delta) + chloroplast delta on CF0 and EF1 or EF1(-delta) + E. coli delta on EF0. The effect of hybrid constructs on F0 channels is surprising in view of the limited sequence homology between chloroplast and E. coli delta (36% conserved residues including conservative replacements). An analysis of the distribution of the conserved residues at present does not allow us to discriminate between the postulated conformational or proton-conductive roles of subunit delta.

Adenosine Triphosphatases↗
PubMed1990

Myelopathy associated with human T cell lymphotropic virus type I (HTLV-I) in natal, South Africa. A clinical and investigative study in 24 patients.

Unexplained spastic myelopathy in black (Zulu) patients, similar to that seen in the tropics, has previously been described from Natal, South Africa. Following reports linking the human T cell lymphotropic virus type I (HTLV-I) to spastic myelopathy, we undertook a prospective and retrospective search for HTLV-I antibodies in 36 patients who were labelled as having unexplained myelopathy; 24 (66%) were positive and HTLV-I was isolated from 4 out of the 6 patients whose peripheral blood lymphocytes were cultured. Eighteen (75%) gave a short history (less than 6 months). There was a female preponderance (71%), spinothalamic dysfunction was common (55%) and as many as half were severely disabled (50% wheelchair bound). Routine laboratory studies showed no specific trends apart from hypergammaglobulinaemia and CSF pleocytosis (greater than 5 cells/microliter in 66% of patients). The total CSF protein was raised (greater than 0.4 g/l) in 45% of patients. The IgG index was greater than 0.7 in 15 of 19 patients. Conventional myelography did not show any specific abnormalities. Computer assisted myelography was undertaken in 22 patients; 3 showed arachnoiditis and 2 spinal cord atrophy. Periventricular lucencies were seen in 1 of 10 patients who had computed tomography of the head. Nerve conduction studies demonstrated abnormalities in 46% of the patients indicating that subclinical peripheral nerve dysfunction was common. Visual evoked responses were abnormal in only 1 patient but brainstem auditory evoked response studies showed some abnormality in 42% of the patients. The finding of HTLV-I antibodies in a significant number, and the isolation of HTLV-I from the blood in 6 of our black patients with noncompressive myelopathy, represents a substantial clinical advance. Future studies should define more clearly the role of the virus in this disorder.

Blotting, Western↗
PubMed1990

Activation of the human leukocyte proteinases elastase and cathepsin G by various surfactants.

A systematic study comprising 28 synthetic ionic and nonionic surfactants was carried out in order to examine their effect on the activity of elastase and cathepsin G from human leukocytes against 4-nitroanilide substrates. The whole spectrum, ranging from a complete loss to a pronounced rise in enzymatic activity, was observed at a 0.1% (w/v) surfactant concentration. Most significantly, benzalkonium chloride led to a five-fold increase in elastase activity.

Anilides↗
PubMed1989

Cross-reconstitution of the F0F1-ATP synthases of chloroplasts and Escherichia coli with special emphasis on subunit delta.

F0F1-ATP synthases catalyse ATP formation from ADP and Pi by using the free energy supplied by the transmembrane electrochemical potential of the proton. The delta subunit of F1 plays an important role at the interface between the channel portion F0 and the catalytic portion F1. In chloroplasts it can plug the protonic conductance of CF0 and in Escherichia coli it is required for binding of EF1 to EF0. We wanted to know whether or not delta of one species was effective between F0 and F1 of the other species and vice versa. To this end the respective coupling membrane (thylakoids, everted vesicles from E. coli) was (partially) depleted of F1 and purified F1, F1(-delta), and delta were added in various combinations to the F1-depleted membranes. The efficiency or reconstitution was measured in thylakoids via the rate of phenazinemethosulfate-mediated cyclic photophosphorylation and in E. coli everted vesicles via the degree of 9-amino-6-chloro-2-methoxyacridine fluorescence quenching. Addition of CF1 to partially CF1-depleted thylakoid vesicles restored photophosphorylation to the highest extent. CF1(-delta)+chloroplast delta, EF1, EF1(-delta)+E. coli delta were also effective but to lesser extent. CF1(-delta)+E. coli delta and EF1(-delta)+chloroplast delta restored photophosphorylation to a small but still significant extent. With F1-depleted everted vesicles prepared by repeated EDTA treatment of E. coli membranes, addition of CF1, CF1 (-delta)+chloroplast delta and CF1(-delta)+E. coli delta gave approximately half the extent of 9-amino-6-chloro-2-methoxyacridine fluorescence quenching as compared to EF1 or EF1(-delta)+E. coli delta by energization of the vesicles with NADH, while Ef1(-delta)+chloroplast delta was ineffective. All 'mixed' combinations were probably reconstitutively active only by plugging the protonic leak through the exposed F0 (structural reconstitution) rather than by catalytic activity. Nevertheless, the cross-reconstitution is stunning in view of the weak sequence similarity between chloroplast delta and E. coli delta. It favors a role of delta as a conformational transducer rather than as a proton conductor between F0 and F1.

Chloroplasts↗
PubMed1989

Chloroplast ATP synthase contains one single copy of subunit delta that is indispensable for photophosphorylation.

F0F1 ATP synthases synthesize ATP in their F1 portion at the expense of free energy supplied by proton flow which enters the enzyme through their channel portion F0. The smaller subunits of F1, especially subunit delta, may act as energy transducers between these rather distant functional units. We have previously shown that chloroplast delta, when added to thylakoids partially depleted of the coupling factor CF1, can reconstitute photophosphorylation by inhibiting proton leakage through exposed coupling factor CF0. In view of controversies in the literature, we reinvestigated two further aspects related to subunit delta, namely (a) its stoichiometry in CF0CF1 and (b) whether or not delta is required for photophosphorylation. By rocket immunoelectrophoresis of thylakoid membranes and calibration against purified delta, we confirmed a stoichiometry of one delta per CF0CF1. In CF1-depleted thylakoids photophosphorylation could be reconstituted not only by adding CF1 and subunit delta but, surprisingly, also by CF1 (-delta). We found that the latter was attributable to a contamination of CF1 (-delta) preparations with integral CF1. To lesser extent CF1 (-delta) acted by complementary rebinding to CF0 channels that were closed because they contained delta [CF0(+delta)]. This added catalytic capacity to proton-tight thylakoid vesicles. The ability of subunit delta to control proton flow through CF0 and the absolute requirement for delta in restoration of photophosphorylation suggest an essential role of this small subunit at the interface between the large portions of ATP synthase: delta may be part of the coupling site between electrochemical, conformational and chemical events in this enzyme.

Amino Acids↗
PubMed1988

Isolation of a new human herpesvirus producing a lytic infection of helper (CD4) T-lymphocytes in peripheral blood lymphocyte cultures--another cause of acquired immunodeficiency?

A new human helper (CD4) T-lymphotropic herpesvirus (HTLHV) was first isolated in February 1985 from the cultured peripheral blood lymphocytes (PBL) of a patient with the acquired immunodeficiency syndrome, and subsequently from the PBL of 1 patient with hairy cell leukaemia and 2 patients with lymphoproliferative disease associated with human T-lymphotropic virus type I infection. The viruses could be serially subcultured in umbilical cord PBL cultures in which they infected helper (CD4) T-lymphocytes producing multinucleate giant cells with intranuclear inclusions followed by cell lysis. Electron microscopy of infected cultures revealed that the isolates were herpesviruses. Specific DNA probing showed that the 4 isolates were related to one another but were distinct from cytomegalovirus, Epstein-Barr virus, Herpesvirus hominis types 1 and 2, and varicella-zoster virus. HTLHV lyses the same target cell as human immunodeficiency virus in PBL cultures suggesting that it may have a similar potential to cause acquired immune deficiency. The development of an unequivocally diagnostic serological test is a priority, so that the epidemiology and pathogenesis of HTLHV infection can be studied.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Delta subunit of chloroplast coupling factor 1 inhibits proton leakage through coupling factor O.

The ATP synthase of chloroplasts consists of a proton-conducting portion, CF0, and a catalytic portion, CF1. The smaller subunits of CF1, in particular delta, may play a key role in the coupling of proton transport to ATP synthesis. Purified subunit delta, when added to partially CF1-depleted thylakoid membranes, can restore photophosphorylation (Engelbrecht, S., and Junge, W. (1987) Eur. J. Biochem. 172, 213-218). We report here that it does so by blocking proton conduction through CF0. Thylakoids were CF1-depleted by incubation in hypoosmolar NaCl/EDTA solutions. Variation of the NaCl concentrations and of the incubation times not only changed the overall degree of CF1 depletion but also the subunit composition of solubilized CF1, namely CF1 containing delta and CF1(-delta). This was quantified by immunoelectrophoresis and by fast protein liquid chromatography. Proton conduction was measured by flash spectrophotometry by using standard electrochromic and pH-indicating absorption changes. The removal of integral CF1 was correlated with high electric conductance of thylakoid membranes, an increased extent of rapid proton leakage, and loss of ATP synthesis activity, which exceeded the percentual loss of CF1. The removal of predominantly CF1(-delta) resulted in comparatively lesser effects on the loss of ATP synthesis and on the extent and velocity of proton leakage. On the same line, addition of integral CF1 and of purified delta diminished the electric leak in CF1-depleted thylakoids. Both approaches, the controlled removal of CF1 and CF1(-delta), respectively, and addition of delta and CF1 showed that delta can act as a "stopcock" to the exposed proton channel CF0.

Adenosine Triphosphate↗
PubMed1988

Isolation of human T-lymphotropic virus type I (HTLV-I) from a black South African with Kaposi's sarcoma.

Serological evidence for HTLV-I infection in the South African population has now been confirmed by the isolation of the virus from the peripheral blood lymphocytes of an adult Tsonga male. The subject was an indigenous black man from the south-eastern Transvaal who had suffered from Kaposi's sarcoma for a decade and in whom serum antibodies against HTLV-I were demonstrated. T-lymphocyte cell lines were established from his peripheral blood lymphocytes and shown to be productively infected with HTLV-I as evidenced by: the characteristic cell morphology; the typical viral morphogenesis on ultra-thin section electron microscopy; the viral genome in DNA extracted from the cell lines; characteristic reverse transcriptase activity and viral specific proteins in the cell culture supernatant fluids. Spread of infection occurs through sexual intercourse, from mother to child, and by blood transfusion. Donated blood should be screened to contain the spread of HTLV-I infection.

Black or African American↗
PubMed1988

Purified subunit delta of chloroplast coupling factor CF1 reconstitutes photophosphorylation in partially CF1-depleted membranes.

The ATP synthase of chloroplasts consists of the proton channel, CF0, and the catalytic part, CF1, which carries nucleotide-binding sites on subunits alpha and beta. The still poorly understood interaction between CF0 and the catalytic sites on CF1 is mediated by the smaller subunits gamma, delta and epsilon of CF1. We investigated the ability of purified delta to block proton leakage through CF0 channels after their exposure by removal of the CF1 counterpart. Thylakoids were partially depleted of CF1 by EDTA treatment. This increased their proton permeability and thereby reduced the rate of photophosphorylation. Subunit delta was isolated and purified by FPLC [Engelbrecht, S. and Junge, W. (1987) FEBS Lett. 219, 321-325]. Addition of delta to EDTA-treated thylakoids reconstituted high rates of phenazine-methosulfate-mediated photophosphorylation. Since delta does not interact with nucleotides by itself, the reconstitution was due to a reduction of the proton leakage through open CF0 channels. The molar ratio of purified delta over exposed CF0, which started to elicit this effect, was 3:1. However, if delta was added together with purified CF1 lacking delta, in a 1:1 molar ratio, the relative amount over exposed CF0 was as low as 0.06. This corroborated our previous conclusion [Lill, H., Engelbrecht, S., Schönknecht, G. and Junge, W. (1986) Eur. J. Biochem. 160, 627-634] that only a very small fraction of exposed CF0 was actually proton-conducting but with a very high unit conductance. CF1 including delta was apparently rebound preferentially to open CF0 channels. Although the ability of delta to control proton conduction through CF0 was evident, it remains to be established whether delta acts as a gated proton valve or as a conformational transducer in the integral CF0CF1 ATPase.

Adenosine Triphosphate↗
PubMed1986

The proton channel, CF0, in thylakoid membranes. Only a low proportion of CF1-lacking CF0 is active with a high unit conductance (169 fS).

We investigated the conductance of pea thylakoid membranes and their capacity for photophosphorylation as function of the extraction of chloroplast coupling factor CF1. The degree of extraction was varied via the incubation time in EDTA-containing hypo-osmolar medium and was measured by rocket electroimmunodiffusion. The conductance of thylakoid membranes was measured by flash kinetic spectrophotometry. The time course of extraction followed the time course of thylakoid swelling. Contrary to expectation increasing loss of CF1 did not primarily increase the velocity of proton efflux from each vesicle. Instead proton-tight vesicles were converted to leaky ones, which lost phosphorylating activity. Two subpopulations occurred, although both types of vesicles, leaky and proton-tight ones, were CF1-depleted to a similar degree. This implied that only a small fraction of CF1-lacking CF0 was functional as a proton channel. Tight vesicles had no functional channels while leaky ones had at least one. We determined the proportion of tight vesicles in three independent ways: via the residual phosphorylation activity, via measurements of proton efflux and via measurements of the electric relaxation across the membrane. The results obtained were identical. A statistical evaluation of the data led us to the following conclusions. EDTA treatment produced vesicles containing approximately 10(5) chlorophyll molecules, equivalent to a total of approximately 100 CF0CF1 per vesicle. Even at the highest degree of extraction (75% of total CF1 extracted) only 2.5 out of 75 exposed CF0 per vesicle were proton-conducting. The unit conductance of one open CF0 channel was 169 +/- 18 fS at pH 7.5 and room temperature. At an electrical driving force of 100 mV this was equivalent to the passage of approximately 10(5) protons/s. The most important consequence of this relatively high unit conductance was that a single open CF0 channel was capable of dissipating the protonmotive force of one vesicle, thereby deactivating the whole remaining catalytic capacity of this vesicle.

Edetic Acid↗