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Low-molecular-weight chromium-binding substance (LMWCr) may bind and carry Cr(III) from the endosome
Journal of Inorganic Biochemistry ( IF 3.9 ) Pub Date : 2021-07-22 , DOI: 10.1016/j.jinorgbio.2021.111555
Kyle C Edwards 1 , Michael W Gannon 1 , Patrick A Frantom 1 , John B Vincent 1
Affiliation  

Trivalent chromium has been proposed to be transported in vivo from the bloodstream to the tissues via endocytosis by transferrin (Tf), the major iron transport protein in the blood. While Cr(III) loss from the Tf/Tf receptor complex after acidification to pH 5.5 has recently been shown to be sufficiently rapid to be physiologically relevant, the released Cr(III) still must exit the endosome during the time of the endocytosis cycle (circa 15 min). Cr(III) binds too slowly to small ligands such as citrate or ascorbate, or even EDTA, for such complexes to form and be transported from the endosome, while no trivalent ion transporters are known. However, the apo form of the peptide low-molecular-weight chromium-binding substance (LMWCr) can remove Cr(III) from Cr(III)2-Tf at neutral pH, albeit slowly, and LMWCr is known to be transported from cells after binding Cr(III), although the transporter is not known. LMWCr subsequently carries Cr(III) to the bloodstream ultimately for removal from the body in the urine. The rate of binding of Cr(III) to apoLMWCr was significantly enhanced in the presence of the Tf/Tf receptor complex. These results suggest that apoLMWCr may function to bind Cr(III) released in the endosomes for ultimate removal from the body as part of a Cr(III) detoxification process.



中文翻译:

低分子量铬结合物质 (LMWCr) 可以结合并携带来自内体的 Cr(III)

已提出三价铬通过转铁蛋白 (Tf)(血液中主要的铁转运蛋白)的内吞作用在体内从血流转运至组织。虽然酸化至 pH 值 5.5 后 Tf/Tf 受体复合物的 Cr(III) 损失最近已被证明足够快以具有生理相关性,但释放的 Cr(III) 仍然必须在内吞作用期间离开核内体循环。大约 15 分钟)。Cr(III) 与柠檬酸盐或抗坏血酸盐或什至 EDTA 等小配体结合太慢,无法形成此类复合物并从内体转运,而目前尚无三价离子转运蛋白。然而,肽低分子量铬结合物质 (LMWCr) 的 apo 形式可以从 Cr(III) 2中去除 Cr(III)-Tf 在中性 pH 条件下,尽管缓慢,并且已知 LMWCr 在结合 Cr(III) 后从细胞中转运,尽管转运蛋白未知。LMWCr 随后将 Cr(III) 携带到血液中,最终通过尿液从体内去除。在存在 Tf/Tf 受体复合物的情况下,Cr(III) 与 apoLMWCr 的结合率显着提高。这些结果表明,apoLMWCr 可能起到结合内体释放的 Cr(III) 的作用,作为 Cr(III) 解毒过程的一部分,最终从体内清除。

更新日期:2021-07-24
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