The Role of Energy Coupling in the Transport of β-Galactosides by Escherichia coli
25 May 1966-Journal of Biological Chemistry (American Society for Biochemistry and Molecular Biology)-Vol. 241, Iss: 10, pp 2200-2211
TL;DR: Evidence was consistent with the hypothesis that the same membrane carriers were involved in active transport by control cells and facilitated diffusion by poisoned cells, and the most striking finding was that the addition of metabolic inhibitors reduced the KT of exit about two orders of magnitude, whereas the Kt of entrance remained constant.
About: This article is published in Journal of Biological Chemistry.The article was published on 1966-05-25 and is currently open access. It has received 390 citations till now. The article focuses on the topics: Lactose transport & Facilitated diffusion.
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TL;DR: In this paper, the authors made an experimental study of the cytoplasm of Escherichia coli and used parameters from cells and cell extracts to calculate approximate activity coefficients for the thermodynamic activity of cellular components.
1,148 citations
TL;DR: Results demonstrate that active export of tetracycline is a common component of the mechanism for tetrACYcline resistance encoded by different plasmid-borne determinants in bacteria.
Abstract: Tetracycline resistance encoded by four genetically different determinants residing on plasmids in Escherichia coli was shown to be associated in each case with an energy-dependent decrease in accumulation of the antibiotic in whole cells in which resistance had been induced. The different class determinants examined were those on plasmids RP1 (class A), R222 (class B), R144 (class C), and RA1 (class D). This decrease in accumulation was attributable to an active efflux, because everted (inside-out) membrane vesicles made from tetracycline-induced E. coli cells containing any one of the four plasmids were shown to concentrate tetracycline by an active influx. This active uptake was not seen in inside-out vesicles from sensitive cells or uninduced R222-containing cells. In vesicles from induced R222-containing cells, the efflux appeared to be carrier-mediated with a Km of about 6 microM. These results demonstrate that active export of tetracycline is a common component of the mechanism for tetracycline resistance encoded by different plasmid-borne determinants in bacteria.
593 citations
TL;DR: Energy Transductions in Mitochondria and the Role of the Membrane in Motility, Bacteriocins and the Energized State are studied.
Abstract: INTRODUCTION ............................................................ A NOTE ONTERMINOLOGY. ENERGY TRANSDUCTIONS IN MITOCHONDRIA ......................... Theories of Energy Conservation ............................................ Chemical coupling hnpothesis ............................................. Conformational coupling .................................................. Chemiosmotic hypothesis ................................................ Point and Counterpoint ..................................................... Permeability of the mitochondrial membrane to protons .................... Vectorial organization of respiratory catalysts ............................. Proton extrusion and the generation of a membrane potential ............... The coupling device: ATPase and ion translocation ........................ Uncoupling and proton conduction ........................................ Fluorescent molecules as probes of the energized state ...................... Metabolite Transport by Mitochondria ...................................... Accumulation of calcium .................................................. Accumulation of potassium ............................................... Transport of phosphate and substrate anions .............................. Summary: Energy Transductions in Mitochondria ........................... ENERGY TRANSFORMATIONS IN BACTERIAL MEMBRANES............ Structural Basis ........................................................... Oxidative Phosphorylation .................................................. General features of respiration and phosphorylation ........................ Coupling factors: the role of ATPase ...................................... Nature of phosphorylating particles from bacterial membranes ............. Coupling of respiration to phosphorylation ................................. Photosynthetic Phosphorylation ............................................. Coupling of Metabolism to Transport ........................................ Transport systems and carriers ........................................... Group translocation ...................................................... Kinetic approach to energy coupling ....................................... Coupling of transport to the respiratory chain in membrane vesicles. Ion gradients and energy coupling ......................................... Role of the Membrane in Motility ............................................ Bacteriocins and the Energized State ........................................ SUMMARY AND PROSPECT .............................................. LITERATURE CITED ....................................................... 172 174 175 175 176 176 177 180 180 180 181 182 183 184 185 185 186 188 189 190 191 193 193 195 196 199 200 201 201 202 205 207 210 214 215 216 216
491 citations
TL;DR: It is indicated that methotrexate transport in the L1210 cell is carrier-mediated and uphill, and the implication of these findings with respect to the development of more effective folic acid antagonists is considered.
398 citations
TL;DR: Increasing levels of resistance to tetracycline and to a number of other unrelated antibiotics, including chloramphenicol, beta-lactams, puromycin, and nalidixic acid, occurred in Escherichia coli after 50 to 200 generations of growth in the presence of subinhibitory concentrations of tetrACYcline or chlorampshenicol.
Abstract: Increasing levels of resistance to tetracycline and to a number of other unrelated antibiotics, including chloramphenicol, beta-lactams, puromycin, and nalidixic acid, occurred in Escherichia coli after 50 to 200 generations of growth in the presence of subinhibitory concentrations of tetracycline or chloramphenicol. In the absence of selective pressure, resistances fell to low levels within 100 generations of growth. This amplification of resistance was observed in laboratory and naturally occurring E. coli strains as well as in polA and recA strains. With the exception of previously identified cmlA and cmlB mutations, tetracycline or chloramphenicol resistances were not P1 transducible. Coincident with the emergence of resistance was the appearance of a previously cryptic energy-dependent efflux system for tetracycline. The expression of resistance phenotypes and the tetracycline efflux system were temperature sensitive at 42 degrees C.
360 citations
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TL;DR: It is shown that the flow-induced uphill transport is a feature characteristic for mobile carrier systems only and is not to be expected in systems in which the substrate is bound to a fixed membrane component ("adsorption membrane"), although such a system may yield identical transport kinetics.
Abstract: 1. In a membrane transport system containing a mobile carrier with affinities for two substrates a concentration gradient with respect to one of the substrates under certain conditions is able to induce an "uphill" transport (against the concentration gradient) of the other. 2. In a kinetic treatment quantitative conditions for such a "flow-induced uphill transport" and some of its characteristics are derived. 3. Experimentally the uphill transport of labelled glucose induced by a concentration gradient for mannose or unlabelled glucose is demonstrated in the human red cell. 4. It is shown that the flow-induced uphill transport is a feature characteristic for mobile carrier systems only and is not to be expected in systems in which the substrate is bound to a fixed membrane component ("adsorption membrane"), although such a system may yield identical transport kinetics. Also with respect to Ussing's flux ratio the two systems are different, the adsorption membrane meeting Ussing's criterion, the carrier membrane not. 5. It is concluded that the transport system in the human red cells must contain a mobile carrier, identical for glucose and mannose.
250 citations