| Autor: |
Bai, Ruoli, Covell, David G., Pei, Xue-Feng, Ewell, John B., Nguyen, Nga Y., Brossi, Arnold, Hamel, Ernest |
| Zdroj: |
Journal of Biological Chemistry; December 2000, Vol. 275 Issue: 51 p40443-40452, 10p |
| Abstrakt: |
2-Chloroacetyl-2-demethylthiocolchicine (2CTC) and 3-chloroacetyl-3-demethylthiocolchicine (3CTC) resemble colchicine in binding to tubulin and react covalently with β-tubulin, forming adducts with cysteine residues 239 and 354. The adducts at Cys-239 are less stable than those at Cys-354 during formic acid digestion. Extrapolating to zero time, the Cys-239 to Cys-354 adduct ratio is 77:23 for 2CTC and 27:73 for 3CTC. Using energy minimization modeling to dock colchicinoids into the electron crystallographic model of β-tubulin in protofilaments (Nogales, E., Wolf, S. G., and Downing, K. H. (1998) Nature391, 199–203), we found two potential binding sites. At one, entirely encompassed within β-tubulin, the C2- and C3-oxygen atoms of 2CTC and 3CTC overlapped poorly with those of colchicine and thiocolchicine, but distances from the reactive carbon atoms of the analogs to the sulfur atoms of the cysteine residues were qualitatively consistent with reactivity. The other potential binding site was located at the α/β interface. Here, the oxygen atoms of the analogs overlapped well with those of colchicine, but relative distances of the reactive carbons to the cysteine sulfur atoms did not correlate with the observed reactivity. A significant conformational change must occur in the colchicine binding site of tubulin in the transition from the unpolymerized to the polymerized state. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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