Tachezy J, Suchan P, Schrével J, Kulda J
Department of Parasitology, Faculty of Science, Charles University, Prague 2, 128 44, Czech Republic.
Exp Parasitol. 1998 Oct;90(2):155-63. doi: 10.1006/expr.1998.4327.
Iron uptake from a low-molecular-weight chelate Fe(III)-nitriloacetate (Fe-NTA) by anaerobic protozoan parasite Tritrichomonas foetus was investigated and compared with that from iron-saturated lactoferrin and transferrin. The results showed that the iron uptake from Fe-NTA was saturable (Km = 2.7 microM, Vmax = 21.7 fmol. microg-1.min-1) and time, and temperature dependent, thus suggesting involvement of a membrane transport carrier. The accumulation of iron from 59Fe-NTA was inhibited by NaF and iron chelators. Amilorid and inhibitors of endosome acidification did not influence the process. Ascorbate stimulated the uptake while a membrane impermeable chelator of bivalent iron (bathophenanthroline disulfonic acid) was inhibitory, suggesting that prior to transport iron is reduced extracellularly. In accord with this assumption, the reduction of ferric to ferrous iron in the presence of intact T. foetus cells was demonstrated. Dynamics and properties of uptake of iron released from transferrin were similar to those from Fe-NTA, indicating involvement of common mechanisms. Iron uptake from lactoferrin displayed profoundly different characteristics consistent with receptor-mediated endocytosis. Metronidazole-resistant derivative of the investigated T. foetus strain showed marked deficiency in iron acquisition from Fe-NTA and transferrin while its iron uptake from lactoferrin was higher than that of the parent strain. The results presented show that T. foetus possesses at least two independent mechanisms that mediate acquisition of iron.
研究了厌氧原生动物寄生虫胎儿三毛滴虫从低分子量螯合物Fe(III)-次氮基三乙酸盐（Fe-NTA）中摄取铁的情况，并将其与从铁饱和乳铁蛋白和转铁蛋白中摄取铁的情况进行了比较。结果表明，从Fe-NTA摄取铁是可饱和的（Km = 2.7 microM，Vmax = 21.7 fmol·μg-1·min-1），且与时间和温度有关，因此表明存在膜转运载体。NaF和铁螯合剂抑制了59Fe-NTA中铁的积累。阿米洛利和内体酸化抑制剂不影响该过程。抗坏血酸刺激摄取，而二价铁的膜不可渗透螯合剂（bathophenanthroline disulfonic acid）具有抑制作用，这表明在转运之前铁在细胞外被还原。根据这一假设，证明了在完整的胎儿三毛滴虫细胞存在的情况下三价铁向二价铁的还原。从转铁蛋白释放的铁的摄取动力学和特性与从Fe-NTA摄取的相似，表明存在共同机制。从乳铁蛋白摄取铁表现出与受体介导的内吞作用一致的截然不同的特征。所研究的胎儿三毛滴虫菌株的甲硝唑抗性衍生物在从Fe-NTA和转铁蛋白获取铁方面存在明显缺陷，而其从乳铁蛋白摄取铁的能力高于亲本菌株。所呈现的结果表明，胎儿三毛滴虫至少拥有两种独立的介导铁获取的机制。
