Many human pathogens use host cell-surface receptors to attach and invade cells. Often, the host-pathogen interaction affinity is low, presenting opportunities to block invasion using a soluble, high-affinity mimic of the host protein. The Plasmodium falciparum reticulocyte-binding protein homolog 5 (RH5) provides an exciting candidate for mimicry: it is highly conserved and its moderate affinity binding to the human receptor basigin (KD  ≥1 μM) is an essential step in erythrocyte invasion by this malaria parasite. We used deep mutational scanning of a soluble fragment of human basigin to systematically characterize point mutations that enhance basigin affinity for RH5 and then used Rosetta to design a variant within the sequence space of affinity-enhancing mutations. The resulting seven-mutation design exhibited 1900-fold higher affinity (KD approximately 1 nM) for RH5 with a very slow binding off rate (0.23 h-1 ) and reduced the effective Plasmodium growth-inhibitory concentration by at least 10-fold compared to human basigin. The design provides a favorable starting point for engineering on-rate improvements that are likely to be essential to reach therapeutically effective growth inhibition.

中文翻译：

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针对疟疾侵袭蛋白 RH5 的基础模拟抑制剂的设计。


许多人类病原体利用宿主细胞表面受体来附着和侵入细胞。通常，宿主与病原体的相互作用亲和力较低，这为使用宿主蛋白的可溶性高亲和力模拟物来阻止入侵提供了机会。恶性疟原虫网织红细胞结合蛋白同源物 5 (RH5) 为拟态提供了令人兴奋的候选者：它高度保守，其与人类受体基础蛋白 (KD ≥1 μM) 的中等亲和力结合是这种疟原虫入侵红细胞的重要步骤。我们使用人类basigin可溶性片段的深度突变扫描来系统地表征增强basigin对RH5亲和力的点突变，然后使用Rosetta在亲和力增强突变的序列空间内设计一个变体。由此产生的七突变设计对 RH5 的亲和力高出 1900 倍（KD 约为 1 nM），结合速率非常慢（0.23 h-1），并且与 RH5 相比，有效的疟原虫生长抑制浓度至少降低了 10 倍人类基础。该设计为工程上的结合率改进提供了有利的起点，这可能对于实现治疗上有效的生长抑制至关重要。