From signal perception to signal transduction: ligand-induced dimeric switch of DctB sensory domain in solution
From signal perception to signal transduction: ligand-induced dimeric switch of DctB sensory domain in solution
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DOI：
10.1111/j.1365-2958.2010.07069.x
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发表时间：
2010-03-01
影响因子：
3.6
通讯作者：
Wang, Yi-Ping
中科院分区：
文献类型：
--
作者：
Nan, Beiyan;Liu, Xin;Wang, Yi-Ping
紫花苜蓿中华根瘤菌DctB是一种典型的跨膜感觉组氨酸激酶，它能感知C-4-二元酸(DCA)，并调节DCA转运蛋白DCTA的表达。我们先前报道了其周质感受域(DctBp)在apo和琥珀酸结合状态下的晶体结构，这些结构在二聚体水平上显示出显著的构象变化。在这里，我们展示了在溶液中配体诱导的二聚体开关以及DctBp的二聚态与DctB在体内的活性之间的强烈关联。利用定点突变，我们确定了信号感知和转导的重要决定因素。具体地说，我们发现配体结合口袋对于DCA诱导的DctB的‘on’活性是必不可少的。DctBp二聚化界面不同区段的突变可以将全长DctB锁定在“开”或“关”状态，而不受配体结合的影响。综上所述，这些结果表明DctBp的信号感知和转导是通过“配体诱导的二聚体开关”进行的，其中配体结合时二聚体构象的变化负责DctB的信号转导。
P>Sinorhizobium meliloti DctB is a typical transmembrane sensory histidine kinase, which senses C-4-dicarboxylic acids (DCA) and regulates the expression of DctA, the DCA transporter. We previously reported the crystal structures of its periplasmic sensory domain (DctBp) in apo and succinate-bound states, and these structures showed dramatic conformational changes at dimeric level. Here we show a ligand-induced dimeric switch in solution and a strong correlation between DctBp's dimerization states and the in vivo activities of DctB. Using site-directed mutagenesis, we identify important determinants for signal perception and transduction. Specifically, we show that the ligand-binding pocket is essential for DCA-induced 'on' activity of DctB. Mutations at different sections of DctBp's dimerization interface can lock full-length DctB at either 'on' or 'off' state, independent of ligand binding. Taken together, these results suggest that DctBp's signal perception and transduction occur through a 'ligand-induced dimeric switch', in which the changes in the dimeric conformations upon ligand binding are responsible for the signal transduction in DctB.