Müller-Reichert T, Chrétien D, Severin F, Hyman A A
Cell Biology Program, European Molecular Biology Laboratory, Meyerhofstrasse 1, Postfach 1022.09, D-69117, Heidelberg, Germany.
Proc Natl Acad Sci U S A. 1998 Mar 31;95(7):3661-6. doi: 10.1073/pnas.95.7.3661.
Microtubules are dynamic polymers that interconvert between periods of slow growth and fast shrinkage. The energy driving this nonequilibrium behavior comes from the hydrolysis of GTP, which is required to destabilize the microtubule lattice. To understand the mechanism of this destabilization, cryo-electron microscopy was used to compare the structure of the ends of shrinking microtubules assembled in the presence of either GTP or the slowly hydrolyzable analogue guanylyl (alpha,beta)methylenediphosphonate (GMPCPP). Depolymerization was induced by cold or addition of calcium. With either nucleotide, we have observed curled oligomers at the ends of shrinking microtubules. However, GDP oligomers were consistently more curved than GMPCPP oligomers. This difference in curvature between depolymerizing GDP and GMPCPP protofilaments suggests that GTP hydrolysis is accompanied by an increase in curvature of the protofilaments, thereby destabilizing the lateral interactions between tubulin subunits in the microtubule lattice.
微管是动态聚合物，在缓慢生长和快速收缩阶段之间相互转换。驱动这种非平衡行为的能量来自GTP水解，这是使微管晶格不稳定所必需的。为了理解这种不稳定的机制，使用冷冻电子显微镜比较了在GTP或缓慢水解类似物鸟苷酰（α,β）亚甲基二膦酸酯（GMPCPP）存在下组装的收缩微管末端的结构。通过冷却或添加钙诱导解聚。无论使用哪种核苷酸，我们都在收缩微管的末端观察到卷曲的寡聚物。然而，GDP寡聚物始终比GMPCPP寡聚物更弯曲。解聚的GDP和GMPCPP原纤维之间的这种曲率差异表明，GTP水解伴随着原纤维曲率的增加，从而破坏了微管晶格中微管蛋白亚基之间的横向相互作用。
