Genetic analysis of periplasmic binding protein dependent transport in Escherichia coli. Each lobe of maltose-binding protein interacts with a different subunit of the MalFGK2 membrane transport complex.
Genetic analysis of periplasmic binding protein dependent transport in Escherichia coli. Each lobe of maltose-binding protein interacts with a different subunit of the MalFGK2 membrane transport complex.
复制标题
DOI：
10.1006/jmbi.1993.1543
复制
发表时间：
1993-10
影响因子：
5.6
通讯作者：
Lien-I Hor;Howard A. Shuman
中科院分区：
文献类型：
--
作者：
Lien-I Hor;Howard A. Shuman
大肠杆菌能够通过被称为麦芽糖转运系统的ATP结合盒转运蛋白积累麦芽糖和麦芽糖糊精。该转运系统由五种蛋白质组成：外膜中的LamB蛋白;周质麦芽糖结合蛋白（MBP）;两种完整的内膜蛋白MalF和MalG;以及与内膜的细胞质面相关的MalK。先前已经提出，MBP在糖跨内膜运输期间与MalF和MalG相互作用。在两个独立的遗传学研究，这里报道，残基210 MBP已被确定为一个重要的网站，其与MalF的相互作用。在一项研究中，malF突变的等位基因特异性抑制子malF 506被分离出来，并产生了将MBP的残基酪氨酸210改变为天冬氨酸的突变。在另一项研究中，分离出了malE（MBP的结构基因）的显性突变;其中一个将相同的酪氨酸残基（210）改变为半胱氨酸。结果表明，Y210 C MBP突变体也是一个等位基因特异的抑制基因malF 506，而抑制基因MBP等位基因的突变体也表现出显性负性表型。以前，它表明，在残基甘氨酸13和天冬氨酸14的MBP的改变可以导致抑制malG突变体。从这些结果和所描述的，它是可能的，提出了一个简单的模型，其中MBP的氨基末端叶与MalG相互作用和MBP的羧基末端叶与MalF相互作用。残基13、14和210在MBP三维结构上的位置与该模型一致。
Escherichia coli is able to accumulate maltose and maltodextrins by an ATP-binding cassette transporter known as the maltose transport system. This transport system is comprised of five proteins: the LamB protein in the outer membrane; the periplasmic maltose-binding protein (MBP); two integral inner membrane proteins, MalF and MalG; and MalK, which is associated with the cytoplasmic face of the inner membrane. It has been previously suggested that MBP interacts with MalF and MalG during sugar transport across the inner membrane. In two independent genetic studies, reported here, residue 210 of MBP has been identified as an important site for its interaction with MalF. In one study, allele-specific suppressors of a malF mutation, malF506, were isolated and yielded mutations which altered residue tyrosine 210 of MBP to aspartic acid. In the other study, dominant mutations in malE (the structural gene of MBP) were isolated; one of these altered the same tyrosine residue (210) to cysteine. It was shown that the Y210C MBP mutant is also an allele-specific suppressor malF506, and that of the suppressor MBP alleles also exhibited dominant-negative phenotypes. Previously it was shown that alterations at residues glycine 13 and aspartate 14 of MBP can result in suppression of a malG mutant. From these results and those described, it is possible to propose a simple model in which the amino-terminal lobe of MBP interacts with MalG and the carboxy-terminal lobe of MBP interacts with MalF. The locations of residues 13, 14 and 210 on the three-dimensional structure of MBP are in keeping with this model.