Zahed Khatooni (Memorial University of Newfoundland)| Laleh Alisaraie (Memorial University of Newfoundland)
The purpose of this study has been to analyze the effects of cations and their concentrations on conformational changes of γ-tubulin, and consequently, the nucleation mechanism of microtubules, which depends on γ-tubulin and its conformational stability.
The results of molecular dynamics simulations have shown that the curved and intermediate conformations of γ-tubulin are dominant. With the curved conformation of γ-tubulin in the Na+ simulation (i.e., NaCl electrolyte), the movement of important segments of the γ-tubulin forms the inaccessible state of the GTP binding site. In comparison, the GTP binding site in Mg+2 condition (i.e., MgCl2 electrolyte) exhibited the intermediate conformation with the accessible binding site. In addition, the presence of Mg+2 in the binding site contributes to the formation of stronger binding to the amino acids of GTP’s surrounding environment compared to the Zn+2 (ZnCl2) and Na+ (NaCl) conditions.
It was found that γ-tubulin stability in the presence of Mg+2 was shown to be higher than that with other electrolytes (e.g., Na+ and Zn+2). Furthermore, the role of a high-affinity metal site in accommodation of cations and GTP interactions was revealed. The results show that the conformational change work in favor of the lattice model versus the allosteric model, which are two existing theories on the tubulins conformational changes.
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