Cellular Stoichiometry of Chemotaxis Proteins in Sinorhizobium meliloti
Cellular Stoichiometry of Chemotaxis Proteins in Sinorhizobium meliloti
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DOI：
10.1128/jb.00141-20
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发表时间：
2020-07-01
影响因子：
3.2
通讯作者：
Scharf, Birgit E.
中科院分区：
文献类型：
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作者：
Arapov, Timofey D.;Saldana, Rafael Castanda;Scharf, Birgit E.
趋化系统使微生物能够感知它们的直接环境，朝着有益的刺激物移动，远离有害的刺激物。为了更好地了解苜蓿中华根瘤菌（Sinorhizobium meliloti）的趋化系统，对苜蓿中华根瘤菌（Sinorhizobium meliloti）的10种趋化蛋白进行了细胞化学计量分析。草木樨是决定。定量免疫印迹和质谱分析的结合揭示了S.苜蓿根瘤菌与大肠杆菌和枯草芽孢杆菌的差异很大。为了将蛋白质比率与其他系统进行比较，将值标准化为中心激酶CheA。所有鼠伤寒沙门苜蓿属植物趋化蛋白的比例有不同程度的增加。接头蛋白CheW 1和CheW 2与CheA的摩尔比高10倍，可能导致在趋化性阵列中形成仅由CheW组成的环，而不是1：1比例的CheA和CheW。我们假设，较高的比率的CheA的主要响应调节器CheY 2是一个结果的变速电机在S。meliloti，而不是开关型电机。同样，参与信号终止的蛋白质在S.苜蓿草，其利用基于CheA反磷酸化的磷酸盐汇机制来抑制运动反应调节剂，而不是如E. coli和B.枯草杆菌。最后，与CheA相比，调节化学感受器甲基化的切布和切R的丰度增加，表明S.苜蓿草。总的来说，这些结果标志着显着差异的细菌趋化性systems.IMPORTANCE共生土壤细菌苜蓿中华根瘤菌通过固定大气中的氮大大有助于宿主植物的生长。S.苜蓿导致其豆科宿主苜蓿的生物量生产增加，并减少了对环境有害的化学肥料的使用。为了更好地理解趋化性在宿主-微生物相互作用中的作用，细菌趋化性系统的全面目录是至关重要的，包括其组成，功能和调节。S.苜蓿属植物与大肠杆菌和枯草芽孢杆菌中的系统几乎没有相似之处。此外，蛋白质总量明显较低。S.苜蓿表现出不同于已知模型的趋化性系统，其通过引入新的蛋白质，如磷酸盐吸收机制所例示的。
Chemotaxis systems enable microbes to sense their immediate environment, moving toward beneficial stimuli and away from those that are harmful. In an effort to better understand the chemotaxis system of Sinorhizobium meliloti, a symbiont of the legume alfalfa, the cellular stoichiometries of all ten chemotaxis proteins in S. meliloti were determined. A combination of quantitative immunoblot and mass spectrometry revealed that the protein stoichiometries in S. meliloti varied greatly from those in Escherichia coli and Bacillus subtilis. To compare protein ratios to other systems, values were normalized to the central kinase CheA. All S. meliloti chemotaxis proteins exhibited increased ratios to various degrees. The 10-fold higher molar ratio of adaptor proteins CheW1 and CheW2 to CheA might result in the formation of rings in the chemotaxis array that consist of only CheW instead of CheA and CheW in a 1:1 ratio. We hypothesize that the higher ratio of CheA to the main response regulator CheY2 is a consequence of the speed-variable motor in S. meliloti, instead of a switch-type motor. Similarly, proteins involved in signal termination are far more abundant in S. meliloti, which utilizes a phosphate sink mechanism based on CheA retrophosphorylation to inactivate the motor response regulator versus CheZ-catalyzed dephosphorylation as in E. coli and B. subtilis. Finally, the abundance of CheB and CheR, which regulate chemoreceptor methylation, was increased compared to CheA, indicative of variations in the adaptation system of S. meliloti. Collectively, these results mark significant differences in the composition of bacterial chemotaxis systems.IMPORTANCE The symbiotic soil bacterium Sinorhizobium meliloti contributes greatly to host-plant growth by fixing atmospheric nitrogen. The provision of nitrogen as ammonium by S. meliloti leads to increased biomass production of its legume host alfalfa and diminishes the use of environmentally harmful chemical fertilizers. To better understand the role of chemotaxis in host-microbe interaction, a comprehensive catalogue of the bacterial chemotaxis system is vital, including its composition, function, and regulation. The stoichiometry of chemotaxis proteins in S. meliloti has very few similarities to the systems in Escherichia coli and Bacillus subtilis. In addition, total amounts of proteins are significantly lower. S. meliloti exhibits a chemotaxis system distinct from known models by incorporating new proteins as exemplified by the phosphate sink mechanism.