Department of Chemistry "Ugo Schiff" Department of Excellence 2018-2022, University of Florence, via della Lastruccia 2, 50019, Sesto Fiorentino, Italy.
Magnetic Resonance Center (CERM), University of Florence, Luigi Sacconi 6, 50019, Sesto Fiorentino (FI), Italy.
Chemistry. 2021 Oct 21;27(59):14690-14701. doi: 10.1002/chem.202102270. Epub 2021 Sep 15.
Ferritins are nanocage proteins that store iron ions in their central cavity as hydrated ferric oxide biominerals. In mammals, further the L (light) and H (heavy) chains constituting cytoplasmic maxi-ferritins, an additional type of ferritin has been identified, the mitochondrial ferritin (MTF). Human MTF (hMTF) is a functional homopolymeric H-like ferritin performing the ferroxidase activity in its ferroxidase site (FS), in which Fe(II) is oxidized to Fe(III) in the presence of dioxygen. To better investigate its ferroxidase properties, here we performed time-lapse X-ray crystallography analysis of hMTF, providing structural evidence of how iron ions interact with hMTF and of their binding to the FS. Transient iron binding sites, populating the pathway along the cage from the iron entry channel to the catalytic center, were also identified. Furthermore, our kinetic data at variable iron loads indicate that the catalytic iron oxidation reaction occurs via a diferric peroxo intermediate followed by the formation of ferric-oxo species, with significant differences with respect to human H-type ferritin.
铁蛋白是一种纳米笼状蛋白，将铁离子储存在其中心腔中，形成水合氧化铁生物矿化物质。在哺乳动物中，除了构成细胞质大型铁蛋白的 L（轻）链和 H（重）链之外，还鉴定出了另一种铁蛋白，即线粒体铁蛋白（MTF）。人源 MTF（hMTF）是一种功能性同聚 H 样铁蛋白，在其亚铁氧化酶活性部位（FS）中具有亚铁氧化酶活性，在该部位，Fe（II）在氧气存在下被氧化为 Fe（III）。为了更好地研究其亚铁氧化酶特性，我们在这里对 hMTF 进行了时程 X 射线晶体学分析，提供了结构证据，证明了铁离子如何与 hMTF 相互作用及其与 FS 的结合。还鉴定了瞬时铁结合位点，这些位点分布在从铁进入通道到催化中心的笼状路径上。此外，我们在可变铁负载下的动力学数据表明，催化铁氧化反应通过双核过氧中间物发生，然后形成铁-氧物种，与人类 H 型铁蛋白相比存在显著差异。
