Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden.
PLoS One. 2012;7(10):e46992. doi: 10.1371/journal.pone.0046992. Epub 2012 Oct 9.
Iron storage and elimination of toxic ferrous iron are the responsibility of bacterioferritins in bacterial species. Bacterioferritins are capable of oxidizing iron using molecular oxygen and import iron ions into the large central cavity of the protein, where they are stored in a mineralized form. We isolated, crystallized bacterioferritin from the microaerophilic/anaerobic, purple non-sulfur bacterium Blastochloris viridis and determined its amino acid sequence and X-ray structure. The structure and sequence revealed similarity to other purple bacterial species with substantial differences in the pore regions. Static 3- and 4-fold pores do not allow the passage of iron ions even though structural dynamics may assist the iron gating. On the other hand the B-pore is open to water and larger ions in its native state. In order to study the mechanism of iron import, multiple soaking experiments were performed. Upon Fe(II) and urea treatment the ferroxidase site undergoes reorganization as seen in bacterioferritin from Escherichia coli and Pseudomonas aeruginosa. When soaking with Fe(II) only, a closely bound small molecular ligand is observed close to Fe(1) and the coordination of Glu94 to Fe(2) changes from bidentate to monodentate. DFT calculations indicate that the bound ligand is most likely a water or a hydroxide molecule representing a product complex. On the other hand the different soaking treatments did not modify the conformation of other pore regions.
铁的储存和有毒亚铁的消除是细菌物种中菌铁蛋白的责任。菌铁蛋白能够利用分子氧氧化铁，并将铁离子导入蛋白质的大中央腔中，在那里以矿化的形式储存。我们从微需氧/厌氧的紫色非硫细菌 Blastochloris viridis 中分离、结晶了菌铁蛋白，并确定了其氨基酸序列和 X 射线结构。结构和序列与其他紫色细菌物种具有相似性，但在孔区域存在实质性差异。静态的 3 倍和 4 倍孔即使结构动力学可能有助于铁门控，也不允许铁离子通过。另一方面，B 孔在其天然状态下对水和较大的离子是开放的。为了研究铁的导入机制，进行了多次浸泡实验。在 Fe(II)和尿素处理下，亚铁氧化酶位点发生重组，就像大肠杆菌和铜绿假单胞菌的菌铁蛋白一样。当仅用 Fe(II)浸泡时，观察到一个紧密结合的小分子配体靠近 Fe(1)，并且 Glu94 与 Fe(2)的配位从双齿变为单齿。DFT 计算表明，结合的配体很可能是一个水分子或氢氧根离子，代表一个产物复合物。另一方面，不同的浸泡处理并没有改变其他孔区域的构象。
