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EMBO J. 2000 Feb 15;19(4):572-80.

Op18/stathmin caps a kinked protofilament-like tubulin tetramer.

Author information

1
M.E. Müller Institute for Microscopy, Biozentrum, University of Basel, CH-4056 Basel, Switzerland.

Abstract

Oncoprotein 18/stathmin (Op18), a regulator of microtubule dynamics, was recombinantly expressed and its structure and function analysed. We report that Op18 by itself can fold into a flexible and extended alpha-helix, which is in equilibrium with a less ordered structure. In complex with tubulin, however, all except the last seven C-terminal residues of Op18 are tightly bound to tubulin. Digital image analysis of Op18:tubulin electron micrographs revealed that the complex consists of two longitudinally aligned alpha/beta-tubulin heterodimers. The appearance of the complex was that of a kinked protofilament-like structure with a flat and a ribbed side. Deletion mapping of Op18 further demonstrated that (i) the function of the N-terminal part of the molecule is to 'cap' tubulin subunits to ensure the specificity of the complex and (ii) the complete C-terminal alpha-helical domain of Op18 is necessary and sufficient for stable Op18:tubulin complex formation. Together, our results suggest that besides sequestering tubulin, the structural features of Op18 enable the protein specifically to recognize microtubule ends to trigger catastrophes.

PMID:
10675326
PMCID:
PMC305595
DOI:
10.1093/emboj/19.4.572
[Indexed for MEDLINE]
Free PMC Article

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