Physik-Department E22, Zentralinstitut für Medizintechnik, Center for Nanoscience, Technische Universität München, 85748 Garching, Germany.
Proc Natl Acad Sci U S A. 2010 Sep 14;107(37):16101-6. doi: 10.1073/pnas.1000916107. Epub 2010 Aug 24.
The molecular chaperone heat shock protein 90 (Hsp90) is an important and abundant protein in eukaryotic cells, essential for the activation of a large set of signal transduction and regulatory proteins. During the functional cycle, the Hsp90 dimer performs large conformational rearrangements. The transient N-terminal dimerization of Hsp90 has been extensively investigated, under the assumption that the C-terminal interface is stably dimerized. Using a fluorescence-based single molecule assay and Hsp90 dimers caged in lipid vesicles, we were able to separately observe and kinetically analyze N- and C-terminal dimerizations. Surprisingly, the C-terminal dimer opens and closes with fast kinetics. The occupancy of the unexpected C-terminal open conformation can be modulated by nucleotides bound to the N-terminal domain and by N-terminal deletion mutations, clearly showing a communication between the two terminal domains. Moreover our findings suggest that the C- and N-terminal dimerizations are anticorrelated. This changes our view on the conformational cycle of Hsp90 and shows the interaction of two dimerization domains.
热休克蛋白 90（Hsp90）是真核细胞中一种重要且丰富的分子伴侣，对于激活一大组信号转导和调节蛋白是必不可少的。在功能循环中，Hsp90 二聚体经历了很大的构象重排。Hsp90 的瞬时 N 端二聚化已经被广泛研究，前提是 C 端界面稳定二聚化。使用基于荧光的单分子测定法和在脂质囊泡中笼化的 Hsp90 二聚体，我们能够分别观察和分析动力学 N 端和 C 端二聚化。令人惊讶的是，C 端二聚体以快速动力学打开和关闭。结合到 N 端结构域的核苷酸和 N 端缺失突变可以调节意想不到的 C 端开放构象的占有率，这清楚地表明两个末端结构域之间存在通讯。此外，我们的发现表明 C 端和 N 端二聚化是反相关的。这改变了我们对 Hsp90 构象循环的看法，并显示了两个二聚化结构域的相互作用。
