Castelle Cindy J, Roger Magali, Bauzan Marielle, Brugna Myriam, Lignon Sabrina, Nimtz Manfred, Golyshina Olga V, Giudici-Orticoni Marie-Thérèse, Guiral Marianne
CNRS, Aix Marseille Université, BIP UMR 7281, FR 3479, 13402 Marseille, France.
CNRS, Aix Marseille Université, Unité de Fermentation, FR 3479, 13402 Marseille, France.
Biochim Biophys Acta. 2015 Aug;1847(8):717-28. doi: 10.1016/j.bbabio.2015.04.006. Epub 2015 Apr 18.
The extremely acidophilic archaeon Ferroplasma acidiphilum is found in iron-rich biomining environments and is an important micro-organism in naturally occurring microbial communities in acid mine drainage. F. acidiphilum is an iron oxidizer that belongs to the order Thermoplasmatales (Euryarchaeota), which harbors the most extremely acidophilic micro-organisms known so far. At present, little is known about the nature or the structural and functional organization of the proteins in F. acidiphilum that impact the iron biogeochemical cycle. We combine here biochemical and biophysical techniques such as enzyme purification, activity measurements, proteomics and spectroscopy to characterize the iron oxidation pathway(s) in F. acidiphilum. We isolated two respiratory membrane protein complexes: a 850 kDa complex containing an aa3-type cytochrome oxidase and a blue copper protein, which directly oxidizes ferrous iron and reduces molecular oxygen, and a 150 kDa cytochrome ba complex likely composed of a di-heme cytochrome and a Rieske protein. We tentatively propose that both of these complexes are involved in iron oxidation respiratory chains, functioning in the so-called uphill and downhill electron flow pathways, consistent with autotrophic life. The cytochrome ba complex could possibly play a role in regenerating reducing equivalents by a reverse ('uphill') electron flow. This study constitutes the first detailed biochemical investigation of the metalloproteins that are potentially directly involved in iron-mediated energy conservation in a member of the acidophilic archaea of the genus Ferroplasma.
嗜酸嗜铁菌（Ferroplasma acidiphilum）是一种极端嗜酸的古菌，存在于富含铁的生物采矿环境中，是酸性矿山排水中自然存在的微生物群落中的重要微生物。嗜酸嗜铁菌是一种铁氧化菌，属于热原体目（广古菌门），该目中包含了目前已知的最极端嗜酸的微生物。目前，对于嗜酸嗜铁菌中影响铁生物地球化学循环的蛋白质的性质、结构和功能组织了解甚少。我们在此结合了生物化学和生物物理技术，如酶纯化、活性测量、蛋白质组学和光谱学，以表征嗜酸嗜铁菌中的铁氧化途径。我们分离出了两种呼吸膜蛋白复合物：一种850 kDa的复合物，包含一个aa3型细胞色素氧化酶和一个蓝铜蛋白，它直接氧化亚铁并还原分子氧；另一种150 kDa的细胞色素ba复合物，可能由一个双血红素细胞色素和一个 Rieske 蛋白组成。我们初步推测，这两种复合物都参与铁氧化呼吸链，在所谓的上坡和下坡电子流途径中发挥作用，这与自养生活方式一致。细胞色素ba复合物可能通过反向（“上坡”）电子流在再生还原当量方面发挥作用。本研究首次对嗜酸嗜铁菌属嗜酸古菌成员中可能直接参与铁介导的能量守恒的金属蛋白进行了详细的生物化学研究。
