The cellular trafficking pathways that conduct zinc to its sites of binding in functional proteins remain largely unspecified. In this study, the hypothesis was investigated that nonspecific proteomic binding sites serve as intermediates in zinc trafficking. Proteome from pig kidney LLC-PK1 cells contains a large concentration of such sites, displaying an average conditional stability constant of 1010-11, that are dependent on sulfhydryl ligands to achieve high-affinity binding of zinc. As a result, the proteome competes effectively with induced metallothionein for Zn2+ upon exposure of cells to extracellular Zn2+ or during in vitro direct competition. The reaction of added Zn2+ bound to proteome with apo-carbonic anhydrase was examined as a potential model for intracellular zinc trafficking. The extent of this reaction was inversely dependent upon proteome concentration and under cellular conditions thought to be negligible. The rate of reaction was strictly first order in both Zn2+ and apo-carbonic anhydrase, and also considered to be insignificant in cells. Adding the low molecular weight fraction of cell supernatant to the proteome markedly enhanced the speed of this reaction, a phenomenon dependent on the presence of glutathione (GSH). In agreement, inclusion of GSH accelerated the reaction in a concentration-dependent manner. The implications of abundant high-affinity binding sites for Zn2+ within the proteome are considered in relation to their interaction with GSH in the efficient delivery of Zn2+ to functional binding sites and in the operation of fluorescent zinc sensors as a tool to observe zinc trafficking.

中文翻译：

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锌的运输 1. 探索蛋白质组、金属硫蛋白和谷胱甘肽的作用。

将锌传导至其在功能蛋白中的结合位点的细胞运输途径在很大程度上仍未明确。在这项研究中，研究了非特异性蛋白质组结合位点作为锌运输中间体的假设。来自猪肾 LLC-PK1 细胞的蛋白质组包含大量此类位点，显示出 1010-11 的平均条件稳定性常数，这些位点依赖于巯基配体来实现锌的高亲和力结合。因此，在细胞暴露于细胞外 Zn2+ 或在体外直接竞争期间，蛋白质组与诱导的金属硫蛋白有效竞争 Zn2+。添加的与蛋白质组结合的 Zn2+ 与脱辅基碳酸酐酶的反应被检查为细胞内锌运输的潜在模型。这种反应的程度与蛋白质组浓度成反比，并且在细胞条件下被认为可以忽略不计。反应速率在 Zn2+ 和脱辅基碳酸酐酶中都是严格的一级反应，在细胞中也被认为是微不足道的。将细胞上清液的低分子量部分添加到蛋白质组中显着提高了该反应的速度，这种现象取决于谷胱甘肽 (GSH) 的存在。一致地，包含 GSH 以浓度依赖性方式加速反应。蛋白质组中丰富的 Zn2+ 高亲和力结合位点的意义与它们与 GSH 的相互作用有关，这些位点有效地将 Zn2+ 传递到功能性结合位点，以及将荧光锌传感器作为观察锌运输的工具。