Merli Marcelo L, Cirulli Brenda A, Menéndez-Bravo Simón M, Cricco Julia A
Instituto de Biología Molecular y Celular de Rosario (IBR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario UNR, Suipacha 531, S2002LRK Rosario, Argentina.
Instituto de Biología Molecular y Celular de Rosario (IBR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario UNR, Suipacha 531, S2002LRK Rosario, Argentina
Biochem J. 2017 Jun 27;474(14):2315-2332. doi: 10.1042/BCJ20170084.
, the causative agent of Chagas disease, presents a complex life cycle and adapts its metabolism to nutrients' availability. Although is an aerobic organism, it does not produce heme. This cofactor is acquired from the host and is distributed and inserted into different heme-proteins such as respiratory complexes in the parasite's mitochondrion. It has been proposed that energy metabolism relies on a branched respiratory chain with a cytochrome oxidase-type 3 (CO) as the main terminal oxidase. Heme A, the cofactor for all eukaryotic CO, is synthesized via two sequential enzymatic reactions catalyzed by heme O synthase (HOS) and heme A synthase (HAS). Previously, TcCox10 and TcCox15 ( Cox10 and Cox15 proteins) were identified in They presented HOS and HAS activity, respectively, when they were expressed in yeast. Here, we present the first characterization of TcCox15 in , confirming its role as HAS. It was differentially detected in the different stages, being more abundant in the replicative forms. This regulation could reflect the necessity of more heme A synthesis, and therefore more CO activity at the replicative stages. Overexpression of a non-functional mutant caused a reduction in heme A content. Moreover, our results clearly showed that this hindrance in the heme A synthesis provoked a reduction on CO activity and, in consequence, an impairment on survival, proliferation and infectivity. This evidence supports that depends on the respiratory chain activity along its life cycle, being CO an essential terminal oxidase.
恰加斯病的病原体呈现出复杂的生命周期，并使其新陈代谢适应营养物质的可利用性。尽管它是一种需氧生物，但它不产生血红素。这种辅因子是从宿主获取的，并分布并插入到不同的血红素蛋白中，如寄生虫线粒体中的呼吸复合体。有人提出，它的能量代谢依赖于一条分支呼吸链，其中细胞色素c氧化酶3型（CO）作为主要的末端氧化酶。血红素A是所有真核生物CO的辅因子，通过血红素O合酶（HOS）和血红素A合酶（HAS）催化的两个连续酶促反应合成。此前，在它身上鉴定出了TcCox10和TcCox15（Cox10和Cox15蛋白）。当它们在酵母中表达时，分别呈现出HOS和HAS活性。在这里，我们首次对它身上的TcCox15进行了表征，证实了它作为HAS的作用。在不同的发育阶段对其进行差异检测，发现它在增殖形式中更为丰富。这种调节可能反映了在增殖阶段需要更多的血红素A合成，因此需要更多的CO活性。非功能性突变体的过表达导致血红素A含量降低。此外，我们的结果清楚地表明，血红素A合成的这种障碍导致CO活性降低，进而损害其生存、增殖和感染性。这一证据支持了它在其生命周期中依赖呼吸链活性，CO是一种必需的末端氧化酶。
