title: Reconstitution of maltose transport in malB mutants of Escherichia coli through calcium-induced disruptions of the outer membrane.
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.
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000687:Amylopectin / Q000494:pharmacology; D002122:Calcium Chloride / Q000378:metabolism / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D004926:Escherichia coli / Q000378:metabolism* / Q000648:ultrastructure; D029968:Escherichia coli Proteins; D007700:Kinetics; D008320:Maltose / Q000378:metabolism*; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D009113:Muramidase / Q000378:metabolism; D033902:Periplasmic Binding Proteins; D014325:Tromethamine / Q000494:pharmacology
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C461619:MalE protein, E coli; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; C461599:maltose transport system, E coli; D014325:Tromethamine; D008320:Maltose; D000687:Amylopectin; D009113:Muramidase; D002122:Calcium Chloride