Hsp110s are unique and essential molecular chaperones in the eukaryotic cytosol. They play important roles in maintaining cellular protein homeostasis. Candida albicans is the most prevalent yeast opportunistic pathogen that causes fungal infections in humans. As the only Hsp110 in Candida albicans, Msi3 is essential for the growth and infection of Candida albicans. In this study, we have expressed and purified Msi3 in nucleotide-free state and carried out biochemical analyses. Sse1 is the major Hsp110 in budding yeast S. cerevisiae and the best characterized Hsp110. Msi3 can substitute Sse1 in complementing the temperature-sensitive phenotype of S. cerevisiae carrying a deletion of SSE1 gene although Msi3 shares only 63.4% sequence identity with Sse1. Consistent with this functional similarity, the purified Msi3 protein shares many similar biochemical activities with Sse1 including binding ATP with high affinity, changing conformation upon ATP binding, stimulating the nucleotide-exchange for Hsp70, preventing protein aggregation, and assisting Hsp70 in refolding denatured luciferase. These biochemical characterizations suggested that Msi3 can be used as a model for studying the molecular mechanisms of Hsp110s.

Hsp110 是真核细胞质中独特且重要的分子伴侣。它们在维持细胞蛋白质稳态方面发挥着重要作用。白色念珠菌是最常见的酵母机会致病菌，可引起人类真菌感染。 Msi3作为白色念珠菌中唯一的Hsp110，对于白色念珠菌的生长和感染至关重要。在本研究中，我们以无核苷酸状态表达和纯化了Msi3，并进行了生化分析。 Sse1 是芽殖酵母中主要的 Hsp110，也是特征最明确的 Hsp110。 Msi3可以替代Sse1来补充携带SSE1基因缺失的酿酒酵母的温度敏感表型，尽管Msi3与Sse1仅具有63.4%的序列同一性。与这种功能相似性一致，纯化的 Msi3 蛋白与 Sse1 具有许多相似的生化活性，包括以高亲和力结合 ATP、改变 ATP 结合的构象、刺激 Hsp70 的核苷酸交换、防止蛋白质聚集以及协助 Hsp70 重折叠变性的荧光素酶。这些生化特征表明 Msi3 可以作为研究 Hsp110 分子机制的模型。