Caplow M, Reid R
Proc Natl Acad Sci U S A. 1985 May;82(10):3267-71. doi: 10.1073/pnas.82.10.3267.
We propose a role for GTP hydrolysis in microtubule assembly in which the GTPase reaction serves to stabilize tubulin subunits in the microtubule. The GTPase reaction in tubulin subunits containing GTP at microtubule ends is presumed to occur predominately in subunits at one of the interfaces between a cap of GTP-containing tubulin subunit and a core of GDP-containing tubulin subunit in the microtubule, resulting in elongation of the core. The proposed model interprets the effects of GDP on microtubule assembly, using a reaction scheme in which GDP-containing tubulin subunits are able to add to microtubule ends. The model can account for the GTP requirement for microtubule assembly, the GDP inhibition of the rate for microtubule elongation, and the fact that a metastable state exists after the enzymic conversion of GTP to GDP, with microtubules which are at steady state. To account for the fact that the microtubule assembly and disassembly rates are nonlinearly dependent upon the tubulin subunit concentration and for the effects of GDP-containing tubulin subunits on the kinetic properties of microtubules, our scheme includes nonproductive as well as productive binding of GTP- and GDP-containing tubulin subunits. We compare our model with an alternative scheme [Hill, T. L. & Carlier, M. F. (1983) Proc. Natl. Acad. Sci. USA 80, 7234-7238], which interprets the effects of GDP on microtubule assembly using a reaction scheme in which GDP is able to exchange with GTP in GTP-containing tubulin subunits in the microtubule and in which the principal GTPase occurs in GTP-containing tubulin subunits at the microtubule/solution interface.
我们提出了GTP水解在微管组装中的作用，其中GTP酶反应用于稳定微管中的微管蛋白亚基。在微管末端含有GTP的微管蛋白亚基中的GTP酶反应被认为主要发生在微管中含GTP的微管蛋白亚基帽与含GDP的微管蛋白亚基核心之间的一个界面处的亚基中，导致核心伸长。所提出的模型使用一个反应方案来解释GDP对微管组装的影响，在该方案中，含GDP的微管蛋白亚基能够添加到微管末端。该模型可以解释微管组装对GTP的需求、GDP对微管伸长速率的抑制，以及在GTP酶促转化为GDP后存在亚稳态这一事实，此时微管处于稳态。为了解释微管组装和解聚速率非线性依赖于微管蛋白亚基浓度以及含GDP的微管蛋白亚基对微管动力学性质的影响，我们的方案包括含GTP和含GDP的微管蛋白亚基的非生产性以及生产性结合。我们将我们的模型与另一种方案[希尔，T.L. & 卡里尔，M.F.（1983年）美国国家科学院院刊80，7234 - 7238]进行比较，该方案使用一个反应方案来解释GDP对微管组装的影响，在该方案中，GDP能够与微管中含GTP的微管蛋白亚基中的GTP交换，并且主要的GTP酶发生在微管/溶液界面处含GTP的微管蛋白亚基中。
