Figure 4.

Effects of MPSP-001 on in vitro tubulin polymerization and competitive binding of colchicine site. (A) Effects of MPSP-001 (25 μmol/L, 100 μmol/L), Taxol (10 μmol/L), colchicines (10 μmol/L) and vincristine (10 μmol/L) on bovine brain tubulin polymerization were measured turbidimetrically. Changes in absorbance at 340 nm (A340) were measured and plotted as a function of time. (B) MPSP-001 binding to tubulin directly and inhibiting tubulin polymerization. Tubulin was co-incubated with indicated concentrations of VCR and MPSP-001 for 1 h, then 5 μmol/L colchicine was added. The fluorescence was measured by spectrofluorometer. All assays were repeated twice and representative data were shown. (C) Interactions between α,β-tubulin and compound MPSP-001 in the docking complex in 3D pattern. Tubulin was shown in cartoon style with the β and α subunit colored in green and cyan, respectively; compound MPSP-001 was shown in stick style; the residues within 4 Å around compound MPSP-001 were shown in line style. Magenta dashed lines denoted the potential hydrogen bonds. (D) 2D representation were drawn using LIGPLOT. Dashed lines represented hydrogen bonds and spiked residues form hydrophobic contacts with the compound.