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首页> 外文期刊>Journal of Molecular Biology >Interaction of the Hsp110 molecular chaperones from S. cerevisiae with substrate protein.
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Interaction of the Hsp110 molecular chaperones from S. cerevisiae with substrate protein.

机译：酿酒酵母Hsp110分子伴侣与底物蛋白的相互作用。

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摘要

Hsp110 proteins act as nucleotide exchange factors of the molecular chaperone Hsp70 in eukaryotes. In addition, they have been reported to stabilize unfolded proteins for subsequent refolding. Hsp110 proteins belong to the Hsp70 superfamily and, in analogy to Hsp70, the substrate-binding site was proposed to be located at the interface of the beta-sandwich domain and the three-helix-bundle domain. Saccharomyces cerevisiae has two closely related cytosolic isoforms of Hsp110, Sse1p and Sse2p. Under normal growth conditions, Sse1p is the predominant form. Sse2p is induced under stress conditions, such as heat shock. Consistent with these findings, we find that Sse2p has increased temperature stability. Both Sse1p and Sse2p accelerate nucleotide exchange on the yeast Hsp70 Ssa1p. Furthermore, Sse1p and Sse2p effectively compete for binding of unfolded luciferase. In contrast to Sse1p, however, Sse2p fails to stabilize this model substrate under thermal stress for subsequent Hsp70-mediated refolding. Using a domain shuffling approach, we show that both the nucleotide-binding domain and the beta-sandwich domain of Sse1p are required to preserve nonnative luciferase in a folding-competent state. Our findings suggest that Sse1p must undergo partial unfolding for efficient protection of luciferase, and that the beta-sandwich domain of Sse1p acts as an intramolecular chaperone for refolding of the nucleotide-binding domain. Under extreme stress conditions, Sse2p appears to take over the nucleotide exchange factor function of Sse1p and might promote the controlled aggregation of stress-denatured proteins.
机译：Hsp110蛋白充当真核生物中分子伴侣Hsp70的核苷酸交换因子。另外，据报道它们使未折叠的蛋白质稳定用于随后的重新折叠。 Hsp110蛋白属于Hsp70超家族，与Hsp70类似，底物结合位点被提议位于β-三明治结构域和三螺旋束结构域的界面。酿酒酵母具有Hsp110的两个紧密相关的胞质亚型，即Sse1p和Sse2p。在正常生长条件下，Sse1p是主要形式。 Sse2p是在压力条件下诱发的，例如热冲击。与这些发现一致，我们发现Sse2p具有增加的温度稳定性。 Sse1p和Sse2p都加速酵母Hsp70 Ssa1p上的核苷酸交换。此外，Sse1p和Sse2p有效竞争未折叠的荧光素酶的结合。但是，与Sse1p相反，Sse2p无法在热应力下稳定此模型基板，以进行后续的Hsp70介导的重折叠。使用域改组方法，我们显示Sse1p的核苷酸结合结构域和β-三明治结构域都需要将非天然荧光素酶保存在可折叠状态。我们的发现表明，Sse1p必须经过部分展开才能有效保护萤光素酶，并且Sse1p的β夹心结构域充当分子内分子伴侣以重新折叠核苷酸结合结构域。在极端的压力条件下，Sse2p似乎接管了Sse1p的核苷酸交换因子功能，并可能促进应力变性蛋白的受控聚集。

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