Department of Biological Sciences, University of Idaho, Moscow, ID 83844, USA.
Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, Houston, TX 77030, USA.
Genetics. 2021 Mar 31;217(3). doi: 10.1093/genetics/iyab009.
The protein molecular chaperone Hsp90 (Heat shock protein, 90 kilodalton) plays multiple roles in the biogenesis and regulation of client proteins impacting myriad aspects of cellular physiology. Amino acid alterations located throughout Saccharomyces cerevisiae Hsp90 have been shown to result in reduced client activity and temperature-sensitive growth defects. Although some Hsp90 mutants have been shown to affect activity of particular clients more than others, the mechanistic basis of client-specific effects is unknown. We found that Hsp90 mutants that disrupt the early step of Hsp70 and Sti1 interaction, or show reduced ability to adopt the ATP-bound closed conformation characterized by Sba1 and Cpr6 interaction, similarly disrupt activity of three diverse clients, Utp21, Ssl2, and v-src. In contrast, mutants that appear to alter other steps in the folding pathway had more limited effects on client activity. Protein expression profiling provided additional evidence that mutants that alter similar steps in the folding cycle cause similar in vivo consequences. Our characterization of these mutants provides new insight into how Hsp90 and cochaperones identify and interact with diverse clients, information essential for designing pharmaceutical approaches to selectively inhibit Hsp90 function.
热休克蛋白 90（Hsp90）是一种蛋白质分子伴侣，在客户蛋白的生物发生和调节中发挥多种作用，影响细胞生理的众多方面。已经表明，位于酿酒酵母 Hsp90 中的氨基酸改变会导致客户活性降低和温度敏感生长缺陷。尽管一些 Hsp90 突变体已被证明比其他突变体更能影响特定客户的活性，但客户特异性影响的机制基础尚不清楚。我们发现，破坏 Hsp70 和 Sti1 相互作用早期步骤的 Hsp90 突变体，或表现出降低的能力以采用 Sba1 和 Cpr6 相互作用为特征的 ATP 结合封闭构象的突变体，同样破坏了三个不同客户的活性，Utp21、Ssl2 和 v-src。相比之下，似乎改变折叠途径中其他步骤的突变体对客户活性的影响更为有限。蛋白质表达谱分析提供了额外的证据，表明改变折叠周期中相似步骤的突变体在体内引起相似的后果。我们对这些突变体的表征为 Hsp90 和共伴侣如何识别和与不同客户相互作用提供了新的见解，这是设计选择性抑制 Hsp90 功能的药物方法所必需的信息。
