Amadei Matteo, De Lauro Alfredo, Polticelli Fabio, Musci Giovanni, Bonaccorsi di Patti Maria Carmela
Department of Biochemical Sciences 'A. Rossi Fanelli', Sapienza University of Rome, Rome, Italy.
Department of Sciences, University Roma Tre, Rome, Italy.
Biometals. 2025 Jul 21. doi: 10.1007/s10534-025-00725-2.
Ferroportin, the only known cellular iron exporter, belongs to the major facilitator superfamily of transporters, which cycle between inward-open, occluded and outward-open conformations to translocate substrates across membranes. Recently reported cryoEM structures of ferroportin identified two metal-binding sites in the central cavity of the protein, with site S1 that includes residues D39 and H43, while site S2 is formed by C326 and H507. Here we have employed fluorescence spectroscopy to evaluate the binding affinity for cobalt of human ferroportin. The results suggest that S2 has a higher affinity for cobalt than S1. Results are discussed in view of available structural data on the outward-open conformation of Fpn and of a novel structural model of the inward-open conformation, obtained with a custom implementation of AlphaFold 2. We propose a mechanism by which the outward flux of iron could be driven by the different affinity of the two sites.
铁转运蛋白是唯一已知的细胞内铁输出蛋白，属于转运蛋白的主要易化子超家族，该家族在向内开放、封闭和向外开放构象之间循环，以跨膜转运底物。最近报道的铁转运蛋白的冷冻电镜结构在蛋白质的中央腔中确定了两个金属结合位点，位点S1包括残基D39和H43，而位点S2由C326和H507形成。在这里，我们采用荧光光谱法评估人铁转运蛋白对钴的结合亲和力。结果表明，S2对钴的亲和力高于S1。结合铁转运蛋白向外开放构象的现有结构数据以及通过AlphaFold 2的定制实现获得的向内开放构象的新结构模型，对结果进行了讨论。我们提出了一种机制，即两个位点的不同亲和力可以驱动铁的外向通量。
