期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：50
页码：14336-14341
DOI：10.1073/pnas.1610137113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceTau is a neuronal microtubule-associated protein linked to numerous neurodegenerative disorders, including Alzheimers disease. Several lines of evidence support tau aggregation as well as loss of its native interactions with microtubules as contributing to pathology. Here, we explored the largely overlooked first step of microtubule assembly, namely the interaction of tau with soluble tubulin heterodimers. Using single-molecule Forster Resonance Energy Transfer (smFRET), we determine the topological features of tau in complex with tubulin. Our results contrast differences in tau isoforms and underscore the importance of conformational flexibility in tau function. Tau is an intrinsically disordered protein with an important role in maintaining the dynamic instability of neuronal microtubules. Despite intensive study, a detailed understanding of the functional mechanism of tau is lacking. Here, we address this deficiency by using intramolecular single-molecule Forster Resonance Energy Transfer (smFRET) to characterize the conformational ensemble of tau bound to soluble tubulin heterodimers. Tau adopts an open conformation on binding tubulin, in which the long-range contacts between both termini and the microtubule binding region that characterize its compact solution structure are diminished. Moreover, the individual repeats within the microtubule binding region that directly interface with tubulin expand to accommodate tubulin binding, despite a lack of extension in the overall dimensions of this region. These results suggest that the disordered nature of tau provides the significant flexibility required to allow for local changes in conformation while preserving global features. The tubulin-associated conformational ensemble is distinct from its aggregation-prone one, highlighting differences between functional and dysfunctional states of tau. Using constraints derived from our measurements, we construct a model of tubulin-bound tau, which draws attention to the importance of the role of taus conformational plasticity in function.
