title: Cyclostreptin binds covalently to microtubule pores and lumenal taxoid binding sites.
abstract: Cyclostreptin (1), a natural product from Streptomyces sp. 9885, irreversibly stabilizes cellular microtubules, causes cell cycle arrest, evades drug resistance mediated by P-glycoprotein in a tumor cell line and potently inhibits paclitaxel binding to microtubules, yet it only weakly induces tubulin assembly. In trying to understand this paradox, we observed irreversible binding of synthetic cyclostreptin to tubulin. This results from formation of covalent crosslinks to beta-tubulin in cellular microtubules and microtubules formed from purified tubulin in a 1:1 total stoichiometry distributed between Thr220 (at the outer surface of a pore in the microtubule wall) and Asn228 (at the lumenal paclitaxel site). Unpolymerized tubulin was only labeled at Thr220. Thus, the pore region of beta-tubulin is an undescribed binding site that (i) elucidates the mechanism by which taxoid-site compounds reach the kinetically unfavorable lumenal site and (ii) explains how taxoid-site drugs induce microtubule formation from dimeric and oligomeric tubulin.
authors.affiliation: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu 9, Madrid 28040, Spain.
authors.forename: Rubén M
authors.initials: RM
authors.lastname: Buey
authors.forename: Enrique
authors.initials: E
authors.lastname: Calvo
authors.forename: Isabel
authors.initials: I
authors.lastname: Barasoain
authors.forename: Oriol
authors.initials: O
authors.lastname: Pineda
authors.forename: Michael C
authors.initials: MC
authors.lastname: Edler
authors.forename: Ruth
authors.initials: R
authors.lastname: Matesanz
authors.forename: Gemma
authors.initials: G
authors.lastname: Cerezo
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Vanderwal
authors.forename: Billy W
authors.initials: BW
authors.lastname: Day
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Sorensen
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: López
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Andreu
authors.forename: Ernest
authors.initials: E
authors.lastname: Hamel
authors.forename: J Fernando
authors.initials: JF
authors.lastname: Díaz
mesh_terms: D000473:Alkanes / Q000378:metabolism; D000595:Amino Acid Sequence; D001216:Asparagine / Q000378:metabolism; D001665:Binding Sites; D001667:Binding, Competitive; D002219:Carbamates / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D000077143:Docetaxel; D034261:Epothilones / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D007783:Lactones / Q000378:metabolism; D013058:Mass Spectrometry; D008870:Microtubules / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017239:Paclitaxel / Q000378:metabolism / Q000494:pharmacology; D011083:Polycyclic Compounds / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D011753:Pyrones / Q000378:metabolism; D043823:Taxoids / Q000378:metabolism / Q000494:pharmacology; D013912:Threonine / Q000378:metabolism; D014404:Tubulin / Q000737:chemistry / Q000378:metabolism*; D050257:Tubulin Modulators / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000473:Alkanes; D002219:Carbamates; D034261:Epothilones; C408303:FR 182877; C413450:Flutax 2; D007783:Lactones; D011083:Polycyclic Compounds; D011753:Pyrones; D043823:Taxoids; D014404:Tubulin; D050257:Tubulin Modulators; D000077143:Docetaxel; D013912:Threonine; C093787:epothilone A; D001216:Asparagine; C071229:discodermolide; D017239:Paclitaxel; C093788:epothilone B