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  • 1
    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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    Paper (German National Licenses)
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  • 2
    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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    Paper (German National Licenses)
    Fulltext
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