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Proceedings Paper

Sedimentation velocity studies of the vinca-alkaloid-induced self-association of tubulin
Author(s): John J. Correia; Sharon Lobert; Anthony Frankfurter; Coleman A. Boyd; Bojana Vulevic
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Paper Abstract

Vinca alkaloids induce tubulin to self-associate into coiled spirals that further align into sheets and macrotubes. The energetics of spiral formation has been studied by sedimentation velocity in a Beckman Optima XLA analytical ultracentrifuge. The analysis process involves conversion of an absorption based sedimentation pattern into a sedimentation distribution, g(s), and determination of mechanism involving isodesmic ligand-medicated or ligand- mediated plus ligand-facilitated self-association. We have compared the vinca alkaloid-induced self-association of porcine brain tubulin in the presence of 50 (mu) M GTP or GDP. For each drug investigated the affinity is shown to be enhanced by GDP and allosterically linked to GDP/GTP, NaCl and divalent cation binding. These allosteric effectors differentially interact with one another. Thus, GDP enhances self-association over GTP by 0.90 kcal/mol, but the enhancement is reduced to 0.35 kcal/mol by increasing NaCl concentration to 150 mM. High salt stimulates spiral formation but it affects GTP-tubulin preferentially over GDP-tubulin. Divalent cations stimulate spiral formation but GDP-tubulin differentiates between Mg+2, Ca+2, and Mn+2, while GTP-tubulin does not. Divalent cations, Ca+2 and Mn+2, induce spiral condensation and macrotube formation, but this is also inhibited by high salt. The differential action of these effectors suggests an interpretation of the energetics in terms of a structural model where charge localization, binding domains and conformational interactions within and between the tubulin heterodimers are responsible for the observed allosteric effects.

Paper Details

Date Published: 22 May 1997
PDF: 6 pages
Proc. SPIE 2985, Ultrasensitive Biochemical Diagnostics II, (22 May 1997); doi: 10.1117/12.274349
Show Author Affiliations
John J. Correia, Univ. of Mississippi Medical Ctr. (United States)
Sharon Lobert, Univ. of Mississippi Medical Ctr. (United States)
Anthony Frankfurter, Univ. of Virginia (United States)
Coleman A. Boyd, Univ. of Mississippi Medical Ctr. (United States)
Bojana Vulevic, Univ. of Mississippi Medical Ctr. (United States)

Published in SPIE Proceedings Vol. 2985:
Ultrasensitive Biochemical Diagnostics II
Gerald E. Cohn; Gerald E. Cohn; Steven A. Soper, Editor(s)

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