大肠杆菌malB和malA突变体中麦芽糖转运的重建。

Reconstitution of maltose transport in malB and malA mutants of Escherichia coli.

作者信息

Brass J M

出版信息

Ann Microbiol (Paris). 1982 Jan;133A(1):171-80.

Abstract

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.

摘要

用含有25 mM Ca++的10 mM Tris（pH 7.2）对lamB细胞进行3小时预处理，导致麦芽糖转运系统的表观Km值由约100 microM向约15 microM发生Ca++诱导的偏移。与未处理细胞中的麦芽糖转运不同，经Ca++处理的lamB细胞的麦芽糖转运受到抗麦芽糖结合蛋白（MBP）抗体的抑制。钙诱导的外膜通透性增加使得malE突变体在暴露于休克液或纯化的MBP时能够重建麦芽糖转运。根据重建细胞中麦芽糖转运系统的Km判断，重建效率相当高（Km = 5 microM）。Vmax约为野生型的20%。与休克液孵育2分钟至30分钟期间麦芽糖转运的快速增加表明MBP很容易进入经Ca++处理的细胞的周质。洗涤重建细胞后，麦芽糖转运持续至少1小时。令人惊讶的是，在与菌株pop1740 malB、malTc的无细胞提取物孵育后，Ca++处理似乎也能使菌株SF1701 malT::Tn10中的麦芽糖转运部分重建。