Mitchison T J, Kirschner M W
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448.
Cell Biophys. 1987 Dec;11:35-55. doi: 10.1007/BF02797111.
We have considered the partitioning of tubulin between monomer and polymer in the cell under conditions of dynamic instability. Dynamic instability adds to the on and off rate constant of steady-state dynamics' new parameters: (1) the rate at which growing microtubules transit to a shrinking phase; and (2) the rate at which shrinking microtubules transit to the growing phase. Under these conditions the free-monomer concentration in the cell increases with total tubulin if the number of nucleating sites is fixed. If the number of nucleating sites increases at fixed total tubulin, subunits shift from the monomer to the polymer phase. These important properties deviate from the traditional equilibrium and steady-state theories and have important implications for the biosynthetic regulation of tubulin.
我们已经考虑了在动态不稳定性条件下细胞中微管蛋白在单体和聚合物之间的分配情况。动态不稳定性给稳态动力学的开启和关闭速率常数增加了新的参数：（1）生长中的微管转变为收缩阶段的速率；（2）收缩中的微管转变为生长阶段的速率。在这些条件下，如果成核位点的数量固定，细胞中游离单体的浓度会随着微管蛋白总量的增加而增加。如果在微管蛋白总量固定的情况下成核位点的数量增加，亚基会从单体相转移到聚合物相。这些重要特性偏离了传统的平衡和稳态理论，并且对微管蛋白的生物合成调节具有重要意义。
