Bradley Justin M, Bugg Zinnia, Moore Geoffrey R, Hemmings Andrew M, Le Brun Nick E
Centre for Molecular and Structural Biochemistry, School of Chemistry, Pharmacy and Pharmacology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
J Am Chem Soc. 2025 Apr 23;147(16):13699-13710. doi: 10.1021/jacs.5c01337. Epub 2025 Apr 13.
Ferritins play a crucial role in iron homeostasis and detoxification in organisms from all kingdoms of life. They are composed of 24 α-helical subunits arranged around an interior cavity where an iron-containing mineral core can be reversibly stored. Despite decades of study, leading to significant progress in defining the routes of Fe uptake and the mechanism of its subsequent oxidation to Fe at diiron catalytic sites termed ferroxidase centers, the process of core synthesis from the product of ferroxidase center activity remains poorly understood. In large part, this is due to the lack of high-resolution structural data on ferritin cores anchored to their nucleation sites on the inner surface of the protein. Mitochondrial ferritins are atypical of those found in higher eukaryotes in that they are homopolymers in which all subunits contain both a ferroxidase center and a presumed but undefined core nucleation site. Here, in conjunction with a novel method for producing iron-enriched ferritin crystals, we exploit these unusual features to structurally characterize both the nucleation site of mitochondrial ferritin and a pentanuclear, ferrihydrite-like iron-oxo cluster formed there. Kinetic data for wild-type and variant proteins confirmed the functional importance of this site, indicating a critical role for E61 in the transfer of Fe from the ferroxidase center to the nascent mineral core.
铁蛋白在所有生命王国的生物体的铁稳态和解毒过程中发挥着关键作用。它们由24个α-螺旋亚基组成，围绕着一个内部腔室排列，在这个腔室中可以可逆地储存含铁矿物核心。尽管经过了数十年的研究，在确定铁摄取途径以及其在称为铁氧化酶中心的双铁催化位点随后氧化为铁的机制方面取得了重大进展，但从铁氧化酶中心活性产物合成核心的过程仍知之甚少。在很大程度上，这是由于缺乏关于锚定在蛋白质内表面成核位点上的铁蛋白核心的高分辨率结构数据。线粒体铁蛋白不同于高等真核生物中发现的铁蛋白，因为它们是同聚物，其中所有亚基都同时含有一个铁氧化酶中心和一个假定但未明确的核心成核位点。在这里，结合一种生产富含铁的铁蛋白晶体的新方法，我们利用这些不寻常的特征从结构上表征线粒体铁蛋白的成核位点以及在那里形成的一种五核、类铁氢氧化物的铁氧簇。野生型和变体蛋白的动力学数据证实了该位点的功能重要性，表明E61在将铁从铁氧化酶中心转移到新生矿物核心中起着关键作用。
