Structural model of Ma1K, the ABC subunit of the maltose transporter of Escherichia coli -: Implications for mal gene regulation, inducer exclusion, and subunit assembly
Structural model of Ma1K, the ABC subunit of the maltose transporter of Escherichia coli -: Implications for mal gene regulation, inducer exclusion, and subunit assembly
复制标题
DOI：
10.1074/jbc.m107905200
复制
发表时间：
2002-02-01
影响因子：
4.8
通讯作者：
Boos, W
中科院分区：
文献类型：
--
作者：
Böhm, A;Diez, J;Boos, W
我们提出了一个三维模型的麦芽糖，麦芽糖转运的ABC亚基从大肠杆菌和鼠伤寒沙门氏菌。它是基于最近发表的密切相关的热球菌（Thermococcus litoralis MalK）的晶体结构。该模型用于识别影响ABC亚基不同功能的突变位置。分离出6个malK点突变，这些突变特别影响与麦芽糖系统的转录调节因子MalT的相互作用。它们被映射到结构模型上，并定义了一个位于c端调控域暴露表面的MalT相互作用位点。已发表的具有诱导剂排斥不敏感表型的点突变形成一个与MalT相互作用位点相邻并垂直定向的斑块。三个序列基序被确定并可视化，它们在ABC亚基中高度保守，具有扩展的C端。它们在调控结构域和atp酶结构域之间形成一个子结构域，可能在这两个结构域之间的信号转导事件中起重要作用。该区域的突变在MalT调控中仍然完全活跃，但会导致运输缺陷。此外，先前已被证明参与与跨膜亚基MalF和MalG相互作用的氨基酸，以及位于高度保守的n端atp酶结构域的氨基酸也被可视化。通过对MalK- malt相互作用位点上的氨基酸进行结构定向诱变，验证了模型MalK结构的有效性。
We are presenting a three-dimensional model of MalK, the ABC subunit of the maltose transporter from Escherichia coli and Salmonella typhimurium. It is based on the recently published crystal structure of the closely related Thermococcus litoralis MalK. The model was used to identify the position of mutations affecting the different functions of the ABC subunit. Six malK point mutations were isolated specifically affecting the interaction with MalT, the transcriptional regulator of the maltose system. They were mapped on the structural model and define a MalT interaction site that is located on an exposed surface of the C-terminal regulatory domain. Published point mutations that confer an inducer exclusion insensitive phenotype form a patch adjacent to and oriented perpendicularly to the MalT interaction site. Three sequence motifs were identified and visualized that are highly conserved among ABC subunits with extended C termini. They form a subdomain between the regulatory and ATPase domain and might play an important role in signal transduction events between these two domains. Mutations in this domain remain fully active in MalT regulation but cause transport defects. In addition, amino acids that have previously been shown to be involved in the interaction with the transmembranous subunits MalF and MalG and that fall into the highly conserved N-terminal ATPase domain were visualized. The validity of the modeled MalK structure was verified by structure-directed mutagenesis of amino acids located within the proposed MalK-MalT interaction site.