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. 2021 Apr 22;9:656273. doi: 10.3389/fcell.2021.656273

FIGURE 4.

FIGURE 4

Colchicine could impair TBCE-TBCB complex function in the α/β-tubulin heterodimer dissociation process by stabilizing the α-tubulin/β-tubulin interface. (A) Two associated α/β-tubulin heterodimers stabilized by the colchicine molecule (green surface). The GTP form of the α-tubulin monomer and the GDP form of the β-tubulin are displayed in blue and yellow (GTP and GDP surfaces are shown in purple and magenta, respectively), PDB ID 4O2B. (B) Zoom-in view of colchicine (green) at the α/β-tubulin interface, next to the α-tubulin GTP binding pocket, PDB ID 4O2B (Prota et al., 2014). (C) Comparison of the free α/β-tubulin heterodimer (α-tubulin in purple and β-tubulin in gray, PDB ID 1JFF; Löwe et al., 2001), with the α/β-tubulin heterodimer stabilized by colchicine (α-tubulin in blue and β-tubulin in yellow, PDB ID 4O2B; Prota et al., 2014) by aligning the α-tubulin monomers. The presence of colchicine affects the α/β-tubulin interface geometry, as shown with the dash lines. (D) The complex TBCE-TBCB, hold by the interaction between the CAP-Gly domains (TBCE CAP-Gly domain surface in green and TBCB CAP-Gly domain surface in gray), binds the α-tubulin monomer of the α/β-tubulin heterodimer (blue, EMDB-2447; Serna et al., 2015) pushing the TBCE LRR domain (domain surface in coral) toward the β-tubulin monomer (yellow) and distorting the α/β-tubulin interface. The presence of colchicine (green surface) could impair α/β-tubulin heterodimer dissociation by stabilizing the α/β-tubulin interface, making it resistant to the mechanical force applied by the LRR domain.