RESUMO
Vinblastine and its derivatives used in clinics as antitumor drugs often cause drug resistance and some serious side effects; thus, it is necessary to study new vinblastine analogues with strong anticancer cytotoxicity and low toxicity. We designed a dimer molecule using two vindoline-bonded dimer vindoline (DVB) and studied its interaction with α,ß-tubulin through the double-sided adhesive mechanism to explore its anticancer cytotoxicity. In our work, DVB was docked into the interface between α-tubulin and ß-tubulin to construct a complex protein structure, and then it was simulated for 100 ns using the molecular dynamics technology to become a stable and refined complex protein structure. Based on such a refined structure, the quantum chemistry at the level of the MP2/6-31G(d,p) method was used to calculate the binding energies for DVB interacting with respective residues. By the obtained binding energies, the active site residues for interaction with DVB were found. Up to 20 active sites of residues within α,ß-tubulin interacting with DVB are labeled in ß-Asp179, ß-Glu207, ß-Tyr210, ß-Asp211, ß-Phe214, ß-Pro222, ß-Tyr224, and ß-Leu227 and α-Asn249, α-Arg308, α-Lys326, α-Asn329, α-Ala333, α-Thr334, α-Lys336, α-Lys338, α-Arg339, α-Ser340, α-Thr349, and α-Phe351. The total binding energy between DVB and α,ß-tubulin is about -251.0 kJ·mol-1. The sampling average force potential (PMF) method was further used to study the dissociation free energy (ΔG) along the separation trajectory of α,ß-tubulin under the presence of DVB based on the refined structure of DVB with α,ß-tubulin. Because of the presence of DVB within the interface between α- and ß-tubulin, ΔG is 252.3 kJ·mol-1. In contrast to the absence of DVB, the separation of pure ß-tubulin needs a free energy of 196.9 kJ·mol-1. The data show that the presence of DVB adds more 55.4 kJ·mol-1 of ΔG to hinder the normal separation of α,ß-tubulin. Compared to vinblastine existing, the free energy required for the separation of α,ß-tubulin is 220.5 kJ·mol-1. Vinblastine and DVB can both be considered through the same double-sided adhesive mechanism to give anticancer cytotoxicity. Because of the presence of DVB, a larger free energy is needed for the separation of α,ß-tubulin, which suggests that DVB should have stronger anticancer cytotoxicity than vinblastine and shows that DVB has a broad application prospect.
RESUMO
Vinblastine (VLB) and its derivatives have been used for clinical first-line drugs to treat various cancers. Due to the resistance and serious side effects from using VLB and its derivatives, there is a need to discover and develop novel VLB derivatives with high activity against cancer cells. In order to better discover and develop new VLB derivatives, we need to study the structural basis of VLB's anti-cancer cytotoxicity and the mechanism of its interaction with α,ß-tubulins. Based on the crystal structure of α,ß-microtubule complex protein, the molecular dynamics method including the sampling PMF method was used to study the variation of dissociation free energy (ΔG) of α,ß-tubulins under different system conditions, and then from which to study the mechanism of the interaction between VLB and α,ß-tubulins. The obtained results show that the dissociation of pure α,ß-tubulins requires 197.8 kJ·mol-1 for ΔG. When the VLB molecule exists between the interface of α,ß-tubulins, the dissociation ΔG of α,ß-tubulins reaches 220.5 kJ·mol-1, which is greater than that of pure α,ß-tubulin. The VLB molecule is formed by connecting a vindoline moiety (VM) molecule with a catharanthine moiety (CM) molecule through a carbon-carbon bond, which is a larger molecule. When the CM molecule exists in the middle of α,ß-tubulin interface, the dissociation ΔG of α,ß-tubulins is 46.2 kJ·mol-1, during which the CM moves with ß-tubulin. When the VM molecule exists between the middle of α,ß-tubulin interface, the dissociation ΔG of α,ß-tubulins is 86.7 kJ·mol-1, during which it moves with α-tubulin. Therefore, the VLB molecule is like a double-sides tape to stick α-tubulin and ß-tubulin together. The VLB molecule intervenes the dynamic equilibrium between dissociation and aggregation of α-tubulin and ß-tubulin by a double-sides sticking mechanism to exert high activity with toxicity against cancer cell. Besides, our results demonstrate that VLB has its structural basis for anticancer cytotoxicity due to its two compositions composed of a CM molecule and a VM molecule although they have little toxicity against cancer cell alone.
