title: In vitro mechanism study of microtubule assembly inhibition by cis-dichlorodiammine-platinum(II).
abstract: The inhibitions of microtubule protein (MTP) and tubulin 6S polymerizations by cis-dichlorodiammine-platinum(II) (CDDP) have been investigated by turbidity measurements and electron microscopy. For 2.5 X 10(-4) M CDDP after 40 min contact time at 27 degrees, the inhibition was 60% for MTP (1.2 mg/ml) and nearly 90% for tubulin 6S (1.2 mg/ml). Microtubules were not present after a 1 hr contact time at 27 degrees with 2.5 X 10(-4) M CDDP. Free sulfhydryl group determinations with 5,5'-dithio-bis-(2-nitrobenzoate) (DTNB) showed that 20.10 (+/- 0.05) sulfhydryl groups were found per tubulin dimer. In the presence of excess CDDP, this number was reduced to 17.74 (+/- 0.05) after a 1 hr contact time at 27 degrees. By using CDDP-tubulin dialysis assays, the CDDP-tubulin complex formation was found to be an irreversible reaction through a covalent binding at the sulfhydryl group sites. By the DEAE filter paper method, CDDP was shown to slightly decrease vinca-alkaloid and colchicine bindings to tubulin likely by inducing a conformational change of the protein.
mesh_terms: D000818:Animals; D002945:Cisplatin / Q000494:pharmacology*; D003078:Colchicine / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D008868:Microtubule Proteins / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects*; D011485:Protein Binding / Q000187:drug effects; D013552:Swine; D014404:Tubulin / Q000378:metabolism; D014748:Vinca Alkaloids / Q000378:metabolism
chemical_list: D046911:Macromolecular Substances; D008868:Microtubule Proteins; D014404:Tubulin; D014748:Vinca Alkaloids; D003545:Cysteine; D002945:Cisplatin; D003078:Colchicine