Ecker D J, Emery T
J Bacteriol. 1983 Aug;155(2):616-22. doi: 10.1128/jb.155.2.616-622.1983.
Double radioactive label transport assays with iron, chromium, and gallium chelates were used to investigate the mechanism of iron uptake by Ustilago sphaerogena. In iron-deficient cells, ferrichrome A iron was taken up without appreciable uptake of the ligand. Iron-sufficient cells partially accumulated the ligand with the metal. The chromium- and gallium-containing analogs of ferrichrome A were transported as intact chelates. Ferrichrome A iron uptake was inhibited by dipyridyl. The data suggest that the intact ferrichrome A chelate binds to a specific receptor, the iron is then separated from the ligand at the membrane by reduction, and the metal is released to the inside of the cell while the ligand is released to the exterior. The reduction step is not transport rate limiting. Iron chelated to citrate was taken up by an energy-dependent process. The citrate ligand was not taken up with the metal. Uptake was sensitive to dipyridyl and ferrozine. Chromic ion chelated to citrate was not transported, suggesting that the iron, rather than the chelate, is recognized by the receptor or that reduction of the metal is required for transport.
采用铁、铬和镓螯合物的双放射性标记转运试验来研究球形黑粉菌摄取铁的机制。在缺铁细胞中，高铁载体A铁被摄取，而配体没有明显摄取。铁充足的细胞会部分积累与金属结合的配体。高铁载体A的含铬和含镓类似物作为完整螯合物被转运。二吡啶抑制高铁载体A铁的摄取。数据表明，完整的高铁载体A螯合物与特定受体结合，然后铁在膜上通过还原与配体分离，金属释放到细胞内部，而配体释放到外部。还原步骤不是转运速率的限制因素。与柠檬酸螯合的铁通过能量依赖过程被摄取。柠檬酸配体不与金属一起被摄取。摄取对二吡啶和亚铁嗪敏感。与柠檬酸螯合的铬离子不被转运，这表明受体识别的是铁而不是螯合物，或者金属的还原是转运所必需的。
