INTA, Laboratorio de Bioinformática y Expresión Génica, Universidad de Chile, El Libano 5524, Macul, Santiago, Chile.
Biochem Biophys Res Commun. 2011 Mar 25;406(4):633-7. doi: 10.1016/j.bbrc.2011.02.109.
Copper is a micronutrient that is required for proper metabolic functioning of most prokaryotic and eukaryotic organisms. To sustain an adequate supply of copper, a cell requires molecular mechanisms that control the metal content to avoid copper toxicity. This toxicity comes primarily from the reactivity of copper, which can lead to the generation of free radicals. In bacteria, two independent systems are responsible for maintaining the balance of copper within the cells (Cop and Cut family proteins). Previous studies describe CutC as a member of the Cut family that is probably involved in copper homeostasis. However, the role of CutC in copper homeostasis is still unclear. In this work, a homolog of CutC was studied in Enterococcus faecalis, a bacterial model for copper homeostasis. The molecular 3D model of efCutC shows the presence of triose phosphate isomerase (TIM) barrel motifs, previously described in CutC crystals from other organisms, which illustrates the conservation of amino acids with the potential ability to coordinate copper. Through quantitative real-time PCR (qPCR), it was demonstrated that efcutC expression is induced late by copper stimulus, Interestingly this transcriptional response directly correlates with a significant increase in the intracellular copper concentration when the protein is absent in the bacteria, suggesting its participation in mechanisms related to efflux of the metal. Our results describe efCutC as a protein able to respond transcriptionally to copper and to participate in the control of copper homeostasis in E. faecalis. This bacterium is the first reported organism containing a cop operon and an active member of the Cut protein family.
铜是一种微量元素，大多数原核和真核生物的新陈代谢功能都需要铜。为了维持足够的铜供应，细胞需要控制金属含量的分子机制，以避免铜毒性。这种毒性主要来自铜的反应性，铜会导致自由基的产生。在细菌中，有两个独立的系统负责维持细胞内铜的平衡（Cop 和 Cut 家族蛋白）。先前的研究描述 CutC 是 Cut 家族的一个成员，可能参与铜稳态。然而，CutC 在铜稳态中的作用尚不清楚。在这项工作中，研究了肠球菌中 CutC 的同源物，肠球菌是铜稳态的细菌模型。efCutC 的分子 3D 模型显示存在磷酸丙糖异构酶（TIM）桶基序，这在来自其他生物体的 CutC 晶体中已有描述，这说明了与潜在铜配位能力相关的氨基酸的保守性。通过实时定量 PCR（qPCR），证明 efcutC 的表达在受到铜刺激后晚期被诱导。有趣的是，这种转录反应与细菌中缺乏该蛋白时细胞内铜浓度的显著增加直接相关，表明其参与了与金属外排相关的机制。我们的结果将 efCutC 描述为一种能够对铜进行转录响应并参与控制肠球菌铜稳态的蛋白质。这种细菌是第一个报道含有 cop 操纵子和活性 Cut 蛋白家族成员的生物体。
