Sensory mechanism of oxygen sensor FixL from Rhizobium meliloti:: Crystallographic, mutagenesis and resonance Raman spectroscopic studies
Sensory mechanism of oxygen sensor FixL from Rhizobium meliloti:: Crystallographic, mutagenesis and resonance Raman spectroscopic studies
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DOI：
10.1006/jmbi.2000.3954
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发表时间：
2000-08-11
影响因子：
5.6
通讯作者：
Shiro, Y
中科院分区：
文献类型：
--
作者：
Miyatake, H;Mukai, M;Shiro, Y
根瘤菌FixL （Rhizobium meliloti, RmFixL）是一种双组份系统的传感器组氨酸激酶，根据O-2水平调节根瘤中固氮相关基因的表达。FixL （RmFixLH）含有血红素（fe -卟啉）作为传感位点，在1.4埃分辨率下测定了其传感域的晶体结构。基于结构和光谱分析，我们提出了不同于BjFixLH的O-2传感机制：弯曲结合的O-2和Ile209侧链之间的空间排斥力引起的F/G环的构象变化将传递到组氨酸激酶结构域。在RmFixLH的共振拉曼光谱中也观察到铁结合的O-2和Ile209之间的相互作用，结果表明，由于Ile209被Ala残基取代，Fe-O-2和Fe-CN的拉伸频率分别从575到570 cm（-1）和504到499 cm（-1）。在RmFixL的I209A突变体中，O-2传感活性被破坏，从而证实了我们提出的机制。(C) 2000年学术出版社。
FixL of Rhizobium meliloti (RmFixL) is a sensor histidine kinase of the two-component system, which regulates the expression of the genes related to nitrogen fixation in the root nodule in response to the O-2 levels. The crystal structure of the sensor domain of FixL (RmFixLH), which contains a heme (Fe-porphyrin) as a sensing site, was determined at 1.4 Angstrom resolution. Based on the structural and spectroscopic analyses, we propose the O-2 sensing mechanism that differs from the case proposed in BjFixLH as follows; conformational changes in the F/G loop, which are induced by steric repulsion between the bent-bound O-2 and the Ile209 side-chain, would be transmitted to the histidine kinase domain. Interaction between the iron-bound O-2, and Ile209 was also observed in the resonance Raman spectra of RmFixLH as evidenced by the fact that the Fe-O-2 and Fe-CN stretching frequencies were shifted from 575 to 570 cm(-1) (Fe-O-2), and 504 to 499 cm(-1), respectively, as the result of the replacement of Ile209 with an Ala residue. In the I209A mutant of RmFixL, the O-2 sensing activity was destroyed, thus confirming our proposed mechanism. (C) 2000 Academic Press.