Frataxin is a mitochondrial protein whose deficiency is the cause of Friedreich's ataxia, a hereditary neurodegenerative disease. This protein plays a role in iron–sulfur cluster biosynthesis, protection against oxidative stress and iron metabolism. In an attempt to provide a better understanding of the role played by metals in its metabolic functions, the mechanisms of mitochondrial metal binding to frataxin in vitro have been investigated. A purified recombinant yeast frataxin homolog Yfh1 binds two Cu(II) ions with a K_d1(Cu^II) of 1.3 × 10⁻⁷ M and a K_d2(Cu^II) of 3.1 × 10⁻⁴ M and a single Cu(I) ion with a higher affinity than for Cu(II) (K_d(Cu^I) = 3.2 × 10⁻⁸ M). Mn(II) forms two complexes with Yfh1 (K_d1(Mn^II) = 4.0 × 10⁻⁸ M; K_d2(Mn^II) = 4.0 × 10⁻⁷ M). Cu and Mn bind Yfh1 with higher affinities than Fe(II). It is established for the first time that the mechanisms of the interaction of iron and copper with frataxin are comparable and involve three kinetic steps. The first step occurs in the 50–500 ms range and corresponds to a first metal uptake. This is followed by two other kinetic processes that are related to a second metal uptake and/or to a change in the conformation leading to thermodynamic equilibrium. Frataxin deficient Δyfh1 yeast cells exhibited a marked growth defect in the presence of exogenous Cu or Mn. Mitochondria from Δyfh1 strains also accumulated higher amounts of copper, suggesting a functional role of frataxin in vivo in copper homeostasis.

中文翻译：

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铁和铜-frataxin相互作用的机制†

Frataxin是一种线粒体蛋白，其缺乏是遗传性神经退行性疾病Friedreich共济失调的原因。该蛋白质在铁硫簇生物合成，防止氧化应激和铁代谢中发挥作用。为了更好地了解金属在其代谢功能中的作用，已研究了线粒体金属在体外与frataxin结合的机制。纯化的重组酵母frataxin同系物Yfh1结合两个Cu（II）离子，其K _d1（Cu ^II）为1.3×10 ^-7 M，一个K _d2（Cu ^II）为3.1×10 ^-4 M，一个Cu（^II）I）离子的亲和力高于Cu（II）（K _d（Cu ^I）= 3.2×10 ^-8 M）。Mn（II）与Yfh1形成两个络合物（K _d1（Mn ^II）= 4.0×10 ^-8 M; K _d2（Mn ^II）= 4.0×10 ^-7 M）。铜和锰以比铁更高的亲和力结合Yfh1（II）。首次确定铁和铜与frataxin的相互作用机理是可比的，并且涉及三个动力学步骤。第一步发生在50-500毫秒范围内，对应于第一次摄取金属。随后是另外两个动力学过程，它们与第二种金属的吸收和/或构象的变化有关，从而导致热力学平衡。在外源铜或锰的存在下，缺乏赤霉素的Δyfh1酵母细胞表现出明显的生长缺陷。Δyfh1菌株的线粒体也积聚了更多的铜，这表明体内frataxin在铜稳态中的功能性作用。