Azotobacter vinelandii NIFL is a flavoprotein that modulates transcriptional activation of nitrogen-fixation genes via a redox-sensitive switch
Azotobacter vinelandii NIFL is a flavoprotein that modulates transcriptional activation of nitrogen-fixation genes via a redox-sensitive switch
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DOI：
10.1073/pnas.93.5.2143
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发表时间：
1996-03-05
影响因子：
11.1
通讯作者：
Dixon, R
中科院分区：
文献类型：
--
作者：
Hill, S;Austin, S;Dixon, R
NIFL调节蛋白通过与增强子结合蛋白NIFA的直接相互作用控制固氮（nif）基因的转录激活。体内NIFL对NIFA活性的调节是对外界氧浓度或固定氮水平的响应。纯化后的NIFL的光谱特征和色谱分析表明，它是一种以FAD为假体基的黄蛋白，在二亚硫酸钠的存在下进行还原，在体外厌氧条件下，NIFL的氧化形式抑制NIFA的转录激活，当NIFL处于还原形式时，这种抑制作用被逆转。因此，NIFL是一种氧化还原敏感调节蛋白，可能代表了一种电子转移不与明显的催化活性相结合的黄蛋白。除了作为氧化还原传感器的能力外，NIFL的活性还对腺苷核苷酸，特别是ADP有反应。这种反应覆盖了氧化还原状态对NIFL的影响，并且在缺乏黄素部分的重新折叠的NIFL载脂蛋白中也观察到。这些观察结果表明，能量和氧化还原状态都是体内nif基因调控的重要决定因素。
The NIFL regulatory protein controls transcriptional activation of nitrogen fixation (nif) genes in Azotobacter vinelandii by direct interaction with the enhancer binding protein NIFA. Modulation of NIFA activity by NIFL in vivo occurs in response to external oxygen concentration or the level of fixed nitrogen. Spectral features of purified NIFL and chromatographic analysis indicate that it Is a flavoprotein with FAD as the prosthetic group, which undergoes reduction in the presence of sodium dithionite, Under anaerobic conditions, the oxidized form of NIFL inhibits transcriptional activation by NIFA in vitro, and this inhibition is reversed when NIFL is in the reduced form. Hence NIFL is a redox-sensitive regulatory protein and may represent a type of flavoprotein in which electron transfer is not coupled to an obvious catalytic activity, In addition to its ability to act as a redox sensor, the activity of NIFL is also responsive to adenosine nucleotides, particularly ADP. This response overrides the influence of redox status on NIFL and is also observed with refolded NIFL apoprotein, which lacks the flavin moiety, These observations suggest that both energy and redox status are important determinants of nif gene regulation in vivo.