Energetics of vinca alkaloid interactions with tubulin

Abstract

Publisher Summary This chapter presents a detailed discussion of the energetics of interactions between Vinca rosea L. (vinca) alkaloids, antimitotic chemotherapeutic agents, and tubulin, the major protein constituent of microtubules and the mitotic spindle. Vinca alkaloids induce tubulin to form indefinite spirals and ordered paracrystals that compete with microtubule formation. Drug binding is known to be thermodynamically linked to spiral formation. In vivo , vinca alkaloids cause mitotic arrest at substoichiometric concentrations by acting at the ends of microtubules to diminish dynamic instability in mitotic spindles. It obtains a full thermodynamic description of the energetics of vinca alkaloid-induced tubulin self-association over a range of temperature and buffer conditions for a group of vinca alkaloid congeners. The chapter describes the use of sedimentation velocity, the quantitative fitting of weight average sedimentation coefficient data, and its applicability to extracting the energetics of vinca alkaloid-tubulin interactions. Sedimentation velocity has proven to be the best method for determining vinca alkaloid binding affinities and drug-induced tubulin spiralling potential. It compares results obtained with four clinically useful vinca alkaloid congeners. There is a quantitative description of the impact of allosteric effectors such as guanine nucleotides, pH, salt, and divalent cations on the system. The chapter relates these energetic findings to the structure of tubulin, the structure and dynamics of microtubules, and the implications for antimitotic and antineoplastic effectiveness with specific emphasis on tubulin isotype effects.