Berczi A, Faulk W P
Institute of Biophysics, Hungarian Academy of Sciences, Szeged.
Biochem Int. 1992 Dec;28(4):577-84.
Human placental trophoblast plasma membranes were prepared by differential centrifugation and solubilized in nonionic detergent. Transferrin receptors were isolated from the solubilized membranes by affinity chromatography on diferric transferrin-coupled Sepharose 4B. The trophoblast plasma membrane vesicles demonstrated NADH-ferricyanide oxidoreductive activity. However, NADH-Fe(III) oxidoreductive activity was very weak when Fe(III)-ammonium citrate or diferric transferrin was used as electron acceptor in the presence of bathophenanthroline disulfonate as an indicator of the reaction. After solubilization, only NADH-ferricyanide oxidoreduction was recovered. Affinity chromatography-purified transferrin receptors did not exhibit any measurable oxidoreductase activity. Thus, when these receptors are present in plasma membranes they mediate redox reactions, but biochemically isolated receptors do not mediate such reactions. These observation suggest that transferrin receptors in plasma membranes bind diferric transferrin, and, in an undetermined way, facilitate Fe(III) release so that iron reduction can occur.
人胎盘滋养层细胞膜通过差速离心法制备，并溶解于非离子去污剂中。通过在双铁转铁蛋白偶联的琼脂糖4B上进行亲和层析，从溶解的膜中分离出转铁蛋白受体。滋养层细胞膜囊泡表现出NADH-铁氰化物氧化还原活性。然而，当柠檬酸铁（III）或双铁转铁蛋白作为电子受体，在存在二氮杂菲二磺酸盐作为反应指示剂的情况下，NADH-Fe（III）氧化还原活性非常弱。溶解后，仅恢复了NADH-铁氰化物氧化还原反应。亲和层析纯化的转铁蛋白受体未表现出任何可测量的氧化还原酶活性。因此，当这些受体存在于细胞膜中时，它们介导氧化还原反应，但生化分离的受体不介导此类反应。这些观察结果表明，细胞膜中的转铁蛋白受体结合双铁转铁蛋白，并以一种未确定的方式促进Fe（III）的释放，从而使铁还原能够发生。
