Machupo virus, known to cause hemorrhagic fevers, enters human cells via binding with its envelope glycoprotein to transferrin receptor 1 (TfR). Similarly, the receptor interactions have been explored in biotechnological applications as a molecular system to ferry therapeutics across the cellular membranes and through the impenetrable blood–brain barrier that effectively blocks any such delivery into the brain. Study of the experimental structure of Machupo virus glycoprotein 1 (MGP1) in complex with TfR and glycoprotein sequence homology has identified some residues at the interface that influence binding. There are, however, no studies that have attempted to optimize the binding potential between MGP1 and TfR. In pursuits for finding therapeutic solutions for the New World arenaviruses, and to gain a greater understanding of MGP1 interactions with TfR, it is crucial to understand the structure–sequence relationship driving the interface formation. By displaying MGP1 on yeast surface we have examined the contributions of individual residues to the binding of solubilized ectodomain of TfR. We identified MGP1 binding hot spot residues, assessed the importance of posttranslational N‐glycan modifications, and used a selection with random mutagenesis for affinity maturation. We show that the optimized MGP1 variants can bind more strongly to TfR than the native MGP1, and there is an MGP1 sequence that retains binding in the absence of glycosylation, but with the addition of further amino acid substitutions. The engineered variants can be used to probe cellular internalization or the blood‐brain barrier crossing to achieve greater understanding of TfR mediated internalization.

中文翻译：

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调节马丘波病毒糖蛋白和人转铁蛋白受体之间的结合界面

已知会引起出血热的马丘波病毒通过与其包膜糖蛋白结合到转铁蛋白受体1（TfR）进入人体细胞。同样，在生物技术应用中，受体相互作用已被研究为一种分子系统，可通过细胞膜并通过不可渗透的血脑屏障有效地阻断任何此类药物向大脑的传递，从而将治疗剂运送到细胞表面。对马丘波病毒糖蛋白1（MGP1）与TfR和糖蛋白序列同源性复合的实验结构的研究已经确定了影响结合的一些残基。但是，还没有研究试图优化MGP1和TfR之间的结合潜力。在寻求为新大陆性腺病毒寻找治疗方案的过程中，为了更好地理解MGP1与TfR的相互作用，了解驱动界面形成的结构-序列关系至关重要。通过在酵母表面展示MGP1，我们检查了单个残基对TfR可溶性胞外域结合的贡献。我们确定了MGP1结合热点残基，评估了翻译后的重要性N-聚糖修饰，并使用具有随机诱变作用的选择进行亲和力成熟。我们显示优化的MGP1变体比天然MGP1可以更牢固地结合到TfR，并且有一个MGP1序列在不存在糖基化的情况下仍能保持结合，但还要添加其他氨基酸取代。工程变体可用于探查细胞内在化或血脑屏障穿越，以进一步了解TfR介导的内在化。