Zampanolide, a potent new microtubule-stabilizing agent, covalently reacts with the taxane luminal site in tubulin ?,?-heterodimers and microtubules.

ABSTRACT: Zampanolide and its less active analog dactylolide compete with paclitaxel for binding to microtubules and represent a new class of microtubule-stabilizing agent (MSA). Mass spectrometry demonstrated that the mechanism of action of both compounds involved covalent binding to ?-tubulin at residues N228 and H229 in the taxane site of the microtubule. Alkylation of N228 and H229 was also detected in ?,?-tubulin dimers. However, unlike cyclostreptin, the other known MSA that alkylates ?-tubulin, zampanolide was a strong MSA. Modeling the structure of the adducts, using the NMR-derived dactylolide conformation, indicated that the stabilizing activity of zampanolide is likely due to interactions with the M-loop. Our results strongly support the existence of the luminal taxane site of microtubules in tubulin dimers and suggest that microtubule nucleation induction by MSAs may proceed through an allosteric mechanism.

SUBMITTER: Field JJ 

PROVIDER: S-EPMC3383615 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature