Spectroscopic and redox properties of a CooA homologue from Carboxydothermus hydrogenoformans
Spectroscopic and redox properties of a CooA homologue from Carboxydothermus hydrogenoformans
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DOI：
10.1074/jbc.m409884200
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发表时间：
2005-02-04
影响因子：
4.8
通讯作者：
Aono, S
中科院分区：
文献类型：
--
作者：
Inagaki, S;Masuda, C;Aono, S
CooA是一种CO敏感的转录激活因子，含有一个b型血红素作为其生理效应子CO的敏感位点。在这项研究中，研究了一个新的CooA同系物从Carboxydothermus hydrogenoformans（Ch-CooA）的光谱和氧化还原性质。光谱和诱变研究表明，His-82和N-末端α-氨基是轴向配体的Fe（III）和Fe（II）血红素在Ch-CooA和CO结合后，N-末端α-氨基被CO取代。两个中性配体，His-82和N-末端α-氨基，与Ch-CooA中的Fe（III）血红素配位，而两个带负电荷的配体，Cys-75的硫醇盐和N-末端Pro的氮原子，是Rr-CooA中Fe（III）血红素的轴向配体。的Fe（III）血红素的配位结构的差异，导致在一个大的正移的氧化还原电位的CH-CooA与RR-CooA相比。比较Ch-CooA和Rr-CooA的性质表明，CooA功能的基本要素将是：（i）血红素是Fe（III），Fe（II）和Fe（II）-CO形式的六配位;（ii）N-末端作为轴向配体与血红素配位，以及（iii）CO结合后CO取代与血红素结合的N-末端。
CooA is a CO-sensing transcriptional activator that contains a b-type heme as the active site for sensing its physiological effector, CO. In this study, the spectroscopic and redox properties of a new CooA homologue from Carboxydothermus hydrogenoformans (Ch-CooA) were studied. Spectroscopic and mutagenesis studies revealed that His-82 and the N-terminal alpha-amino group were the axial ligands of the Fe(III) and Fe(II) hemes in Ch-CooA and that the N-terminal a-amino group was replaced by CO upon CO binding. Two neutral ligands, His-82 and the N-terminal alpha-amino group, are coordinated to the Fe(III) heme in Ch-CooA, whereas two negatively charged ligands, a thiolate from Cys-75 and the nitrogen atom of the N-terminal Pro, are the axial ligands of the Fe(III) heme in Rr-CooA. The difference in the coordination structure of the Fe(III) heme resulted in a large positive shift of redox potentials of Ch-CooA compared with Rr-CooA. Comparing the properties of Ch-CooA and Rr-CooA demonstrates that the essential elements for CooA function will be: (i) the heme is six-coordinate in the Fe(III), Fe(II), and Fe(II)-CO forms; (ii) the N-terminal is coordinated to the heme as an axial ligand, and (iii) CO replaces the N-terminal bound to the heme upon CO binding.