Reconstitution of maltose transport in malB and malA mutants of Escherichia coli.
Pretreatment of lamB cells for 3 h with 10 mM Tris, pH 7.2, containing 25 mM Ca++ resulted in a Ca++-induced shift of the apparent Km of the maltose transport system from about 100 microM to about 15 microM. In contrast to maltose transport in untreated cells, that of Ca++-treated lamB cells was inhibited by anti-MBP (maltose-binding protein) antibodies. The calcium-induced permeability increase of the outer membrane allowed reconstitution of maltose transport in a malE mutant upon exposure to shock fluid or purified MBP. The efficiency of reconstitution, as judged by the Km of the maltose transport system in reconstituted cells, was rather high (Km = 5 microM). Vmax was around 20% of the wild-type. The rapid increase in maltose transport between 2' and 30' of incubation with shock fluid indicated that MBP readily entered the periplasm of Ca++-treated cells. Maltose transport continued for at least 1 h after washing the reconstituted cells. Surprisingly, Ca++ treatment also seemed to allow partial reconstitution of maltose transport in strain SF1701 malT::Tn10 after incubation with cell-free extracts of strain pop1740 malB,malTc.[1]References
- Reconstitution of maltose transport in malB and malA mutants of Escherichia coli. Brass, J.M. Ann. Microbiol. (Paris) (1982) [Pubmed]
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