Tubulin, hybrid dimers, and tubulin S. Stepwise charge reduction and polymerization

Bhattacharyya, B. ; Sackett, D. L. ; Wolff, J. (1985) Tubulin, hybrid dimers, and tubulin S. Stepwise charge reduction and polymerization Journal of Biological Chemistry, 260 (18). pp. 10208-10216. ISSN 0021-9258

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Official URL: http://www.jbc.org/content/260/18/10208.abstract?s...


Limited proteolysis of rat brain tubulin (αβ) by subtilisin cleaves a 1-2-kDa fragment from the carboxyl-terminal ends of both the α and β subunits with a corresponding loss in negative charge of the proteins. The β subunit is split much more rapidly (and exclusively at 5 ° C), yielding a protein with cleaved β and intact α subunit, called α βs, which is of intermediate charge. Further proteolysis cleaves the carboxyl terminus of the α subunit leading, irreversibly, to the doubly cleaved product, named tubulin S, with a composition α s β s. Both cleavage products are polymerization-competent and their polymers are resistant to 1 mM Ca2+- and 0.24 M NaCl-induced depolymerization. The two polymers differ in that the αβs polymer is stable to cold, GDP, and podophyllotoxin, whereas tubulin S polymer is disassembled by these agents; moreover, αβs forms ring-shaped polymers, whereas αsβs forms filaments associated into bundles and sheets. Tubulin S co-polymerizes with native tubulin yielding a mixed product of intermediate stability. The presence of low mole fractions of tubulin S leads to a marked reduction in the critical concentration for polymerization of the mixture.

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Source:Copyright of this article belongs to American Society for Biochemistry and Molecular Biology.
ID Code:26144
Deposited On:06 Dec 2010 13:01
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