Chloroacetates of 2- and 3-demethylthiocolchicine: specific covalent interactions with tubulin with preferential labeling of the beta-subunit.
We synthesized two chemically reactive A ring modified analogs of colchicine, 2-chloroacetyl-2-demethylthiocolchicine (2-CTC) and 3-chloroacetyl-3-demethylthiocolchicine (3-CTC). Both are similar to colchicine as inhibitors of tubulin polymerization and act as competitive inhibitors of colchicine binding (apparent Ki values, 3 microM). [14C]-labeled 2-CTC and 3-CTC bound to tubulin at 37 degrees C but not at 0 degree C, and bound drug formed covalent bond(s) with tubulin. The binding and covalent reactions were inhibited by podophyllotoxin. About 60% of the bound 3-CTC rapidly formed a covalent bond with tubulin. With 2-CTC the covalent reaction was slower than the binding reaction, and only one-third of the bound 2-CTC reacted covalently with tubulin. The ratio of radiolabel in beta-tubulin to that in alpha-tubulin was about 4:1 with both 2-CTC and 3-CTC.
Grover
S
S
Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Boyé
O
O
Getahun
Z
Z
Brossi
A
A
Hamel
E
E
D001667:Binding, Competitive; D003078:Colchicine / Q000031:analogs & derivatives* / Q000737:chemistry; D066298:In Vitro Techniques; D013329:Structure-Activity Relationship; D014404:Tubulin / Q000737:chemistry*
D014404:Tubulin; C076932:3-chloroacetyl-3-demethylthiocolchicine; C076931:2-chloroacetyl-2-demethylthiocolchicine; D003078:Colchicine