The essential eukaryotic chaperone Hsp90 regulates the form and function of diverse client proteins, many of which govern thermotolerance, virulence, and drug resistance in fungal species. However, use of Hsp90 inhibitors as antifungal therapeutics has been precluded by human host toxicities and suppression of immune responses. We recently described resorcylate aminopyrazoles (RAPs) as the first class of Hsp90 inhibitors capable of discriminating between fungal (Cryptococcus neoformans, Candida albicans) and human isoforms of Hsp90 in biochemical assays. Here, we report an iterative structure–property optimization toward RAPs capable of inhibiting C. neoformans growth in culture. In addition, we report the first X-ray crystal structures of C. neoformans Hsp90 nucleotide binding domain (NBD), as the apoprotein and in complexes with the non-species-selective Hsp90 inhibitor NVP-AUY922 and three RAPs revealing unique ligand-induced conformational rearrangements, which reaffirm the hypothesis that intrinsic differences in protein flexibility can confer selective inhibition of fungal versus human Hsp90 isoforms.

中文翻译：

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真菌选择性间苯二酚氨基吡唑 Hsp90 抑制剂：全细胞抗隐球菌活性的优化和隐球菌选择性结构起源的见解

必需的真核伴侣蛋白 Hsp90 调节多种客户蛋白的形式和功能，其中许多控制真菌物种的耐热性、毒力和耐药性。然而，人类宿主毒性和免疫反应抑制已排除了将 Hsp90 抑制剂用作抗真菌治疗剂。我们最近将间苯二酚氨基吡唑 (RAPs) 描述为第一类 Hsp90 抑制剂，能够在生化分析中区分真菌（新型隐球菌、白色念珠菌）和人类 Hsp90 同种型。在这里，我们报告了对能够抑制C. neoformans在培养中生长的 RAP 的迭代结构-性能优化。此外，我们报告了第一个 X 射线晶体结构C. neoformans Hsp90 核苷酸结合结构域 (NBD)，作为载脂蛋白并与非物种选择性 Hsp90 抑制剂 NVP-AUY922 和三种 RAP 复合，揭示了独特的配体诱导的构象重排，这再次证实了蛋白质灵活性的内在差异的假设可以赋予真菌对人类 Hsp90 同种型的选择性抑制。