Bonomi F, Pagani S
Dipartimento di Scienze Molecolari Agroalimentari, Università degli Studi di Milano, Italy.
Eur J Biochem. 1991 Jul 1;199(1):181-6. doi: 10.1111/j.1432-1033.1991.tb16107.x.
A study was made on the uptake of iron by horse spleen apoferritin, by using as an iron source the same ferric dihydrolipoate complex which represents the major product in the anaerobic removal of ferritin-bound iron by dihydrolipoate at neutral pH. The ferric dihydrolipoate complex was chemically synthesized and used as an iron donor to apoferritin. Iron uptake was studied, at slightly alkaline pH and in anaerobic conditions, as a function of the concentration of both the iron donor and apoferritin. Isolation of ferritin from mixtures of ferric dihydrolipoate and apoferritin, and subsequent identification of the oxidation state of ferritin-bound iron, showed that the first metal atoms were taken up in the ferrous form and that this early step was accompanied by accumulation of ferric iron. Total iron uptake increased with the molar ratio of complex to apoprotein and ranged over 25-40% of the iron being supplied. The amount of ferrous iron found inside the protein did not exceed 50-60 mol iron/mol ferritin after a 48-h incubation. At this time, ferric iron represented a significant fraction of the iron found in the isolated ferritin. Analytical and spectroscopic data indicated that fractional rates and equilibria for disassembly of the ferric complex in the presence of apoferritin were independent of the concentration of the protein and of the complex itself.
通过使用相同的二氢硫辛酸铁络合物作为铁源，对马脾脱铁铁蛋白对铁的摄取进行了研究，该络合物是二氢硫辛酸在中性pH下厌氧去除铁蛋白结合铁的主要产物。二氢硫辛酸铁络合物通过化学合成，并用作脱铁铁蛋白的铁供体。在略碱性pH和厌氧条件下，研究了铁摄取作为铁供体和脱铁铁蛋白浓度的函数。从二氢硫辛酸铁和脱铁铁蛋白的混合物中分离铁蛋白，并随后鉴定铁蛋白结合铁的氧化态，结果表明，最初的金属原子以亚铁形式被摄取，并且这一早期步骤伴随着三价铁的积累。总铁摄取量随着络合物与脱辅基蛋白的摩尔比增加而增加，范围为所供应铁的25 - 40%。孵育48小时后，在蛋白质内部发现的亚铁量不超过50 - 60摩尔铁/摩尔铁蛋白。此时，三价铁在分离的铁蛋白中占相当大的比例。分析和光谱数据表明，在脱铁铁蛋白存在下，三价络合物的分解速率分数和平衡与蛋白质和络合物本身的浓度无关。
