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  • Title: Reconstitution of maltose transport in malB mutants of Escherichia coli through calcium-induced disruptions of the outer membrane.
    Author: Brass JM, Boos W, Hengge R.
    Journal: J Bacteriol; 1981 Apr; 146(1):10-7. PubMed ID: 7012112.
    Abstract:
    The barrier function of the Escherichia coli outer membrane against low concentrations of maltose in strains missing the lambda receptor was partially overcome by treating the cells for 3 h with 25 mM Ca2+. Kinetic analysis of maltose-transport revealed a Ca2+-induced shift of the apparent Km of the system from about 100 microM in cells pretreated with Tris to about 15 microM in cells pretreated with Tris plus Ca2+. In contrast to maltose transport in untreated cells, that of Ca2+-treated lamB cells was inhibited by molecules with a high molecular weight, such as amylopectin (molecular weight, 20,000), and anti-maltose-binding protein antibodies. In addition, lysozyme was shown to attack Ca2+-treated cells in contrast to untreated cells. The Ca2+-induced permeability increase of the outer membrane allowed reconstitution of maltose transport in a mutant missing the maltose-binding protein with osmotic shock fluid containing the maltose-binding protein. Even though Ca2+-treatment allowed the entry of large molecules, the release of the periplasmic maltose-binding protein or alkaline phosphatase was negligible.
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