Division of Biotechnology, College of Life Sciences & Biotechnology, Korea University, Seoul 136-701, Republic of Korea.
Biochem Biophys Res Commun. 2010 Jan 1;391(1):990-4. doi: 10.1016/j.bbrc.2009.12.003. Epub 2009 Dec 5.
Iron is essential for the survival of organisms, but either excess or deficient levels of iron induce oxidative stress, thereby causing cell damage. As a result, iron regulation is essential for proper cell growth and proliferation in most organisms. Bacterioferritin is a ferritin-like family protein that contains a heme molecule and a ferroxidase site at the di-iron center. This protein plays a primary role in intracellular iron storage for iron homeostasis, as well as in the maintenance of iron in a soluble and non-toxic form. Although several bacterioferritin structures have been determined, no structural studies have successfully elucidated the molecular function of the heme molecule and the ferroxidase center. Here, we report the crystal structure of bacterioferritin from Rhodobacter sphaeroides. This protein exists in a roughly spherical configuration via the assembly of 24 subunits. We describe the oligomeric arrangement, ferroxidase center and heme-binding site based on this structure. The protein contains a single iron-binding configuration in the ferroxidase center, which allows for the release of iron by His130 when the protein is in the intermediate state. The heme molecule in RsBfr is stabilized by shifting of the van der Waals interaction center between the porphyrin of the heme and Trp26. We anticipate that further structural analysis will provide a more complete understanding of the molecular mechanisms of members of the ferritin-like family.
铁是生物体生存所必需的，但铁的含量过高或过低都会诱导氧化应激，从而导致细胞损伤。因此，铁的调节对于大多数生物体中细胞的正常生长和增殖是至关重要的。细菌铁蛋白是一种与铁蛋白类似的家族蛋白，它含有一个血红素分子和一个二铁中心的亚铁氧化酶位点。这种蛋白在细胞内铁储存中起着主要作用，以维持铁的平衡，同时也将铁维持在可溶和无毒的形式。尽管已经确定了几种细菌铁蛋白的结构，但没有结构研究成功阐明了血红素分子和亚铁氧化酶中心的分子功能。在这里，我们报告了来自球形红杆菌的细菌铁蛋白的晶体结构。这种蛋白通过 24 个亚基的组装，以大致球形的构象存在。我们根据这一结构描述了寡聚体排列、亚铁氧化酶中心和血红素结合位点。该蛋白在亚铁氧化酶中心含有一个单一的铁结合构型，当蛋白处于中间状态时，His130 允许铁的释放。RsBfr 中的血红素分子通过血红素卟啉和 Trp26 之间范德华相互作用中心的移动而稳定。我们预计，进一步的结构分析将提供对铁蛋白类似家族成员的分子机制更完整的理解。
