Exploring transferrin-receptor interactions at the single-molecule level
Exploring transferrin-receptor interactions at the single-molecule level
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DOI：
10.1529/biophysj.107.114637
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发表时间：
2008-01-01
影响因子：
3.4
通讯作者：
Ikai, Atsushi
中科院分区：
文献类型：
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作者：
Yersin, Alexandre;Osada, Toshiya;Ikai, Atsushi
铁转运蛋白转铁蛋白（Tf）与其在细胞表面的受体之间的相互作用是大多数生物体的基础。Tf受体（TfR）结合铁负载Tf （holo-Tf）并将其运输到核内体，酸性pH有利于铁的释放。然后，无铁Tf（载脂蛋白Tf）被带回细胞表面并与TfR分离。本文研究了在不同条件下Tf- tfr在单分子水平上的相互作用。用holo-Tf或apo-Tf功能化的原子力显微镜探针探测TfR。我们测试了固定在云母基质上的纯化TfR和活细胞表面的原位TfR。动态力测量显示云母上或细胞表面的TfR有相似的结果，但显示出holo-Tf-TfR和apo-Tf-TfR相互作用之间的显著差异。首先，与载脂蛋白tf -TfR相互作用相比，解除holo-Tf和TfR相互作用所需的力总是更强。其次，holo-Tf-TfR复合物的解离涉及克服两个能量势垒，而载脂蛋白tf - tfr解离途径仅包含一个能量势垒。这些结果与提出全息tf - tfr和载脂蛋白tf - tfr相互作用之间接触点差异的模型一致。
Interaction between the iron transporter protein transferrin (Tf) and its receptor at the cell surface is fundamental for most living organisms. Tf receptor (TfR) binds iron-loaded Tf (holo-Tf) and transports it to endosomes, where acidic pH favors iron release. Iron-free Tf (apo-Tf) is then brought back to the cell surface and dissociates from TfR. Here we investigated the Tf-TfR interaction at the single-molecule level under different conditions encountered during the Tf cycle. An atomic force microscope tip functionalized with holo-Tf or apo-Tf was used to probe TfR. We tested both purified TfR anchored to a mica substrate and in situ TfR at the surface of living cells. Dynamic force measurements showed similar results for TfR on mica or at the cell surface but revealed striking differences between holo-Tf-TfR and apo-Tf-TfR interactions. First, the forces necessary to unbind holo-Tf and TfR are always stronger compared to the apo-Tf-TfR interaction. Second, dissociation of holo-Tf-TfR complex involves overcoming two energy barriers, whereas the apo-Tf-TfR unbinding pathway comprises only one energy barrier. These results agree with a model that proposes differences in the contact points between holo-Tf-TfR and apo-Tf-TfR interactions.