The biosynthesis of heme O and heme A is not regulated by copper.
The biosynthesis of heme O and heme A is not regulated by copper.
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血红素O和血红素A的生物合成不受铜调节。
DOI：
10.1021/bi050893d
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Hegg,EricL
中科院分区：
文献类型：
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作者：
Morrison,MScott;Cricco,JuliaA;Hegg,EricL
血红素A是所有真核生物和许多原核细胞色素氧化酶（CcO）酶的必需辅助因子。尽管它对CcO和电子传递途径具有明显的重要性，但对血红素A的调控基本上一无所知。因为CcO是血红素A的唯一天然靶点，而铜也是CcO活性所必需的，所以人们假设铜可能调节血红素A的稳态。先前报道的工作表明，铜和铁的内稳态通常有很强的联系，间接证据表明铜和血红素a之间可能存在特定的联系。为了解决这个问题，我们进行了实验，严格确定铜是否在血红素a的内稳态中起作用。将血红素B转化为血红素A的两种酶血红素O合成酶（heme O synthase， HOS）和血红素A合成酶（heme A synthase， HAS）分别在酿酒酵母（saccharomyces cerevisiae）中进行基因组表位标记，并通过Western blot分析量化它们在不同铜条件下的表达。这些结果表明，HOS和HAS的转录、翻译和稳定性的总和与铜无关。此外，通过对细胞血红素提取物的分析，研究了细胞内铜浓度对枯草芽孢杆菌（在大肠杆菌中表达）和球形红杆菌HOS和HAS活性的影响。没有观察到细胞内铜的变化趋势。综上所述，我们的研究结果表明，细胞内铜水平不会影响HOS或HAS的转录、翻译、稳定性或活性。
Heme A is an obligatory cofactor in all eukaryotic and many prokaryotic cytochromecoxidase (CcO) enzymes. Despite its obvious importance to CcO and the electron transport pathway, essentially nothing is known concerning the regulation of heme A. Because CcO is the only natural target for heme A and copper is also required for CcO activity, it was postulated that copper might regulate heme A homeostasis. Work reported previously demonstrated that there is often a strong connection between copper and iron homeostasis in general, and circumstantial evidence pointed to a possible specific link between copper and heme A. To address this question, we conducted experiments to determine rigorously whether copper plays a role in heme A homeostasis. The two enzymes responsible for the conversion of heme B to heme A, heme O synthase (HOS) and heme A synthase (HAS), were separately genomically epitope-tagged inSaccharomyces cerevisiae, and their expression under various copper conditions was quantified by Western blot analysis. These results demonstrated that the sum of transcription, translation, and stability of HOS and HAS were independent of copper. Additionally, the effects of intracellular copper concentrations on the activity of HOS and HAS fromBacillus subtilis(expressed inEscherichia coli) andRhodobacter sphaeroideswere examined by analysis of cellular heme extracts. No trends with respect to intracellular copper were observed. In combination, our results demonstrate that intracellular copper levels do not affect the transcription, translation, stability, or activity of either HOS or HAS.