The B-type channel is a major route for iron entry into the ferroxidase center and central cavity of bacterioferritin.
The B-type channel is a major route for iron entry into the ferroxidase center and central cavity of bacterioferritin.
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DOI：
10.1074/jbc.m114.623082
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发表时间：
2015-02-06
期刊：
影响因子：
--
通讯作者：
Mauk AG
中科院分区：
文献类型：
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作者：
Wong SG;Grigg JC;Le Brun NE;Moore GR;Murphy ME;Mauk AG
背景：铁进入原核生物铁蛋白的途径尚不清楚。结果：大肠杆菌细菌铁蛋白B型通道突变导致Fe(II)氧化和矿化速率显著降低。结论：B型通道是铁进入细菌铁蛋白的重要途径。意义：B型通道作为原核铁摄取途径可能具有普遍重要性。细菌铁蛋白是一种细菌铁储存和解毒蛋白，能够在其中央空腔内形成氢氧化铁矿物核心。要做到这一点，铁必须穿过细菌铁蛋白外壳，这预计会通过结构研究确定的一个或多个穿过外壳的通道发生。24个B型通道的大小和负静电势表明，它们可能为铁进入细菌铁蛋白提供了一条途径。将大肠杆菌细菌铁蛋白B型通道(Asn-34、Glu-66、Asp-132和Asp-139)上的残基替换，以确定它们是否对铁核形成重要。在D132F变异体中，观察到铁氧基酶中心的Fe(II)的初始氧化和随后的铁矿化的速率显著降低。这个变体的晶体结构表明，用苯丙氨酸取代残基132引起了B型通道的空间阻塞，而没有其他物质结构的扰动。我们认为，B型通道是铁进入细菌铁蛋白的铁氧酶中心和储铁腔的主要途径。
Background: Routes of iron entry into prokaryote ferritins are unknown. Results: Mutation of the B-type channel of E. coli bacterioferritin resulted in substantially decreased rates of Fe(II) oxidation and mineralization. Conclusion: The B-type channel is an important route for iron entry into bacterioferritin. Significance: B-type channels may be of general importance as routes of iron uptake in prokaryotic ferritins. Bacterioferritin is a bacterial iron storage and detoxification protein that is capable of forming a ferric oxyhydroxide mineral core within its central cavity. To do this, iron must traverse the bacterioferritin protein shell, which is expected to occur through one or more of the channels through the shell identified by structural studies. The size and negative electrostatic potential of the 24 B-type channels suggest that they could provide a route for iron into bacterioferritin. Residues at the B-type channel (Asn-34, Glu-66, Asp-132, and Asp-139) of E. coli bacterioferritin were substituted to determine if they are important for iron core formation. A significant decrease in the rates of initial oxidation of Fe(II) at the ferroxidase center and subsequent iron mineralization was observed for the D132F variant. The crystal structure of this variant shows that substitution of residue 132 with phenylalanine caused a steric blockage of the B-type channel and no other material structural perturbation. We conclude that the B-type channel is a major route for iron entry into both the ferroxidase center and the iron storage cavity of bacterioferritin.