Tau is one of the diverse group of microtubule-associated proteins that bind to microtubules and may thereby influence their structure and function. It occurs in the mammalian brain, mainly in axons, and is a component of the neurofibrillary tangles of Alzheimer's disease. Tau was recently sequenced, but there remains a short-age of structural data on the protein. We have now prepared paracrystals of tau suitable for electron microscopy and image processing. They show distinct transverse banding and polarity, indicating that the protein subunits are aligned with the same orientations. In contrast to other paracrystals, those of tau protein can stretch or contract continuously by more than three-fold; the axial repeats range from 22 to 68 nm. After scaling to a common period, the density distributions are closely superimposable. This suggests that tau is an elastic molecule.
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http://dx.doi.org/10.1038/334359a0 | DOI Listing |
Biochem Pharmacol
September 1999
Institut de Pharmacologie et de Biologie Structurale, C.N.R.S. Toulouse, France.
Vinblastine, vincristine, vindesine, and vinorelbine, the four vinca alkaloids used in cancer therapy, differ in their antitumoral spectra and toxicities, but not in their inhibitory effects on microtubule assembly in vitro. At higher drug concentrations, vinca alkaloids induce the assembly of spiral filaments of tubulin, which, in turn, can interact laterally and form paracrystals. Using methods that distinguish spiral filaments and paracrystals (aggregated spirals), we found that spiral filament formation was largely independent of the incubation temperature, of the alkaloid used, and of the presence or absence of microtubule-associated proteins (MAPs).
View Article and Find Full Text PDFBiophys J
January 1991
Department of Physics, University of Waterloo, Ontario, Canada.
The NMR spin-grouping technique is applied to low hydration oriented fibers of NaDNA to study the role of exchange in determining the apparent (observed) spin relaxation of the system. The analysis proceeds in three steps: first, the apparent proton relaxation is measured at high fields, with both selective and nonselective inversion pulse sequences, and in the rotating frame. The spin-grouping technique is used in all spin-lattice relaxation measurements to provide the optimum apparent relaxation characterization of the sample.
View Article and Find Full Text PDFJ Struct Biol
August 1991
Max-Planck-Unit for Structural Molecular Biology, DESY, Hamburg, Federal Republic of Germany.
Previous studies on tau protein showed that the protein forms paracrystals which are unusually elastic. The paracrystals were obtained from a mixture of isoforms prepared from brain tissue, and the protein was in a mixed state of phosphorylation. Subsequently we showed that the structure and elasticity was related to the state of phosphorylation.
View Article and Find Full Text PDFJ Struct Biol
March 1990
Centro de Biología Molecular (CSIC-UAM), Universidad Autónoma, Madrid, Spain.
A novel type of collagenous fibers has been isolated from human brain and characterized by electron microscopy and optical diffraction. It was found that the morphology of the fibers is similar, but not identical, to that of skin collagen. Also, the collagenous fibers show some similarities with the paracrystals that could be assembled in vitro from purified microtubule-associated protein tau.
View Article and Find Full Text PDFJ Cell Biol
October 1989
Max Planck Unit for Structural Molecular Biology, Hamburg, Federal Republic of Germany.
In a previous report we have shown that microtubule-associated protein tau can be induced to form paracrystals (Lichtenberg, B., E.-M.
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