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  • 1
    Electronic Resource
    Electronic Resource
    Role of cysteine residues in the lac permease of Escherichia coli (1987)
    s.l. : American Chemical Society
    Biochemistry 26 (1987), S. 1132-1136 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00378a022
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of different phospholipids on the reconstitution of two functions of the lactose carrier ofEscherichia coli (1985)
    Springer
    The journal of membrane biology 84 (1985), S. 259-267 
    Details
    ISSN: 1432-1424
    Keywords: proteoliposomes ; counterflow ; lactose carrier ; phospholipid requirement ; Escherichia coli ; reconstitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The lactose carrier was extracted from membranes ofEscherichia coli and transport activity reconstituted in proteoliposomes containing different phospholipids. Two different assays f for carrier activity were utilized: counterflow and membrane potential-driven uptake. Proteoliposomes composed ofE. coli lipid or of 50% phosphatidylethanolamine−50% phosphatidylcholine showed very high transport activity with both assays. On the other hand, proteoliposomes containing asolectin, phosphatilcholine or 25% cholesterol/75% phosphatidylcholine showed good counterflow activity but poor membrane potentialdriven uptake. The discrepancy between the two types of transport activity in the latter group of three lipids is not due to leakiness to protons, size of proteoliposomes, or carrier protein content per proteoliposome. Apparently one function of the carrier molecule shows a broad tolerance for various phospholipids, while a second facet of the membrane protein activity requires very restricted lipid enviroment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871389
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  • 3
    Electronic Resource
    Electronic Resource
    Na+ (Li+)-proline cotransport inEscherichia coli (1985)
    Springer
    The journal of membrane biology 84 (1985), S. 157-164 
    Details
    ISSN: 1432-1424
    Keywords: proline transport ; cation cotransport ; harmaline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Na+ and Li+ were found to stimulate the transport ofl-proline by cells ofEscherichia coli induced for proline utilization. The gene product of the put P gene is involved in the expression of this transport activity since the put P+ strains CSH 4 and WG 148 show activity and the put P− strain RM 2 fails to show this cation coupled transport. The addition of proline was found to stimulate the uptake of Li+ and of Na+. Attempts to demonstrate proline stimulated H+ uptake were unsuccessful. It is concluded that the proline carrier (coded by the put P gene) is responsible for Na+ (or Li+)-proline cotransport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01872213
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  • 4
    Electronic Resource
    Electronic Resource
    Transport by reconstituted lactose carrier from parental and mutant strains ofEscherichia coli (1984)
    Springer
    The journal of membrane biology 79 (1984), S. 185-193 
    Details
    ISSN: 1432-1424
    Keywords: reconstitution ; lactose transport ; membrane potential ; pH gradient ; proteolytic enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The lactose transport carrier from parental (X71/F'W3747) and mutant cells (54/F'5441) was reconstituted into proteoliposomes. Transport by the counterflow assay showed slightly greater activity in proteoliposomes prepared from extracts of the mutant membranes compared with that for the parental cell. The mutant carrier showed a threefold lowerK m but similarV max compared to the parent. On the other hand proteoliposomes from the mutant showed a defect in protonmotive force-driven accumulation, compared with the parent. With a pH gradient (inside alkaline) plus a membrane potential (inside negative) the parental proteoliposomes accumulated lactose 25-fold over the medium concentration while the mutant proteoliposomes accumulated sixfold. In a series of experiments proteoliposomes were exposed to proteolytic enzymes. Chrymotrypsin treatment resulted in 30% inhibition of counterflow activity for the reconstituted carrier from both parent and mutant. Papain produced 84% inhibition of transport by the reconstituted parental carrier but only 41% of that of the mutant. Trypsin and carboxypeptidase Y treatment had no effect on counterflow activity of either parent or mutant. Exposure of purified lactose carrier in proteoliposomes to carboxypeptidase Y resulted in the release of alanine and valine, the two C-terminal amino acids predicted from the DNA sequence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01872122
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  • 5
    Electronic Resource
    Electronic Resource
    ATP synthesis driven by a protonmotive force inStreptococcus lactis (1975)
    Springer
    The journal of membrane biology 25 (1975), S. 285-310 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary An electrochemical potential difference for hydrogen ions (a protonmotive force) was artificially imposed across the membrane of the anaerobic bacteriumStreptococcus lactis. When cells were exposed to the ionophore, valinomycin, the electrical gradient was established by a potassium diffusion potential. A chemical gradient of protons was established by manipulating the transmembrane pH gradient. When the protonmotive force attained a value of 215 mV or greater, net ATP synthesis was catalyzed by the membrane-bound Ca++, Mg++-stimulated ATPase. This was true whether the protonmotive force was dominated by the membrane potential (negative inside) or the pH gradient (alkaline inside). Under these conditions, ATP synthesis could be blocked by the ATPase inhibitor, dicyclohexylcarbodiimide, or by ionophores which rendered the membrane specifically permeable to protons. These observations provide strong evidence in support of the chemiosmotic hypothesis, which states that the membrane-bound ATPase couples the inward movement of protons to the synthesis of ATP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868580
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  • 6
    Electronic Resource
    Electronic Resource
    Membrane transport ofp-nitrophenyl-α-galactoside by the melibiose carrier ofEscherichia coli (1980)
    Springer
    The journal of membrane biology 56 (1980), S. 169-175 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary p-Nitrophenyl-α-galactoside (α-pNPG) was found to be a substrate for the melibiose transport system ofEscherichia coli. This sugar enters induced cells via the carrier and is split by α-galactosidase to galactose andp-nitrophenol. In mutant cells lacking the α-galactosidase [3H]-α-pNPG accumulated to concentrations 15 times higher than the external medium. The transport of α-pNPG is inhibited by both Na+ and Li+. Na+ (10mm) reduced the Km for α-pNPG from 0.45 to 0.18mm and reduced theV max from 6.7 nmoles/min/mg dry wt to a value of 3.0.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01875968
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  • 7
    Electronic Resource
    Electronic Resource
    A protonmotive force as the source of energy for galactoside transport in energy depletedEscherichia Coli (1977)
    Springer
    The journal of membrane biology 31 (1977), S. 233-255 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary An artificially produced electrochemical potential difference for protons (protonmotive force) provided the energy for the transport of galactosides inEscherichia coli cells which were depleted of their endogenous energy reserves. The driving force for the entry of protons was provided by either a transmembrane pH gradient or a membrane potential. The pH gradient across the membrane was created by acidifying the external medium. The membrane potential (inside negative) was established by the outward diffusion of potassium (in the presence of valinomycin) or by the inward diffusion of the permeant thiocyanate ion. The magnitude of the electrochemical potential difference for protons agreed well with magnitude of the chemical potential difference of the lactose analog, thiomethylgalactoside. The observations are consistent with the view that the carrier-mediated entry of each galactoside molecule is accompanied by the entry of one proton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869407
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of lithium ion on melibiose transport inEscherichia coli (1978)
    Springer
    The journal of membrane biology 42 (1978), S. 45-59 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Both Li+ and Na+ stimulated the uptake of thiomethylgalactoside by the melibiose transport system ofEscherichia coli. On the other hand, Li+ inhibited the growth of cells on melibiose as a sole source of carbon. This inhibition was specific for melibiose, and Li+ had no effect on growth of cells on glucose, galactose, lactose, or glycerol. The effect of the cation on melibiose transport was investigated in a mutant which cannot utilize glucose. After entry into this cell, melibiose is cleaved into glucose and galactose by α-galactosidase, and the resulting glucose is excreted. Since the entry step was found to be rate-limiting, glucose production could be taken as a measure of melibiose transport. Li+ inhibited the transport of melibiose, but not the induction of the melibiose operon nor the activity of α-galactosidase. Li+ was found to inhibit the entry ofp-nitrophenyl-α-d-galactoside, but notp-nitrophenyl-β-d-galactoside entry. Thus, the cation specificity for the melibiose membrane carrier varies with different transport substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870393
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  • 9
    Electronic Resource
    Electronic Resource
    THE CATION SPECIFICITY FOR THE MELIBIOSE TRANSPORT SYSTEM OF E. COLI (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 341 (1980), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1980.tb47191.x
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  • 10
    Electronic Resource
    Electronic Resource
    Melibiose-Cation Cotransport System of Escherichia coli (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 456 (1985), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1985.tb14884.x
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