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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Unexpected NO-dependent DNA binding by the CooA homolog from Carboxydothermus hydrogenoformans
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Unexpected NO-dependent DNA binding by the CooA homolog from Carboxydothermus hydrogenoformans

机译：Carboxydothermushydrooformans的CooA同源物意外的NO依赖性DNA结合

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摘要

CooA, the CO-sensing heme protein from Rhodospirillum rubrum, regulates the expression of genes that encode a CO-oxidation system, allowing R. rubrum to use CO as a sole energy source. To better understand the gas-sensing regulation mechanism used by R. rubrum CooA and its homologs in other organisms, we characterized spectroscopically and functionally the Fe(Ⅱ), Fe(Ⅱ)-NO, and Fe(Ⅱ)-CO forms of CooA from Carboxydothermus hydrogenoformans. Surprisingly, and unlike R. rubrum CooA, C hydrogenoformans CooA binds NO to form a six-coordinate Fe(Ⅱ)-NO heme that is active for DNA binding in vitro and in vivo. In contrast, R. rubrum CooA, which is exquisitely specific for CO, forms a five-coordinate Fe(Ⅱ)-NO adduct that is inactive for DNA binding. Based on analyses of protein variants and temperature studies, NO-dependent DNA binding by C. hydrogenoformans CooA is proposed to result from a greater apparent stability of the six-coordinate Fe(Ⅱ)-NO adduct at room temperature. Results from the present study strengthen the proposal that CO specificity in the CooA activation mechanism is based on the requirement for a small, neutral distal ligand, which in turn affects the relative positioning of the ligand-bound heme.
机译：CooA是来自红景天螺旋藻的CO感应血红素蛋白，它调节编码CO氧化系统的基因的表达，从而使R. rubrum能够将CO用作唯一的能源。为了更好地了解红景天CooA及其在其他生物中的同系物的气敏调节机制，我们从光谱和功能上对CooA的Fe（Ⅱ），Fe（Ⅱ）-NO和Fe（Ⅱ）-CO形式进行了表征。来自于羧甲基甲烷。出乎意料的是，与R. rubrum CooA不同，C氢甲酸酯类CooA与NO结合形成六配位的Fe（Ⅱ）-NO血红素，该血红素对体内外DNA结合具有活性。相比之下，对CO特异的R. rubrum CooA形成了五配位的Fe（Ⅱ）-NO加合物，对DNA结合没有活性。基于蛋白质变异体的分析和温度研究，提出了氢福寿螺CooA依赖于NO的DNA结合是由于六配位Fe（Ⅱ）-NO加合物在室温下具有更大的表观稳定性所致。来自本研究的结果加强了这样的建议，即CooA激活机制中的CO特异性是基于对小，中性远侧配体的需求，这反过来会影响配体结合的血红素的相对位置。

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