Theriot J A
Whitehead Institute for Biomedical Research, Cambridge, MA 02142.
Semin Cell Biol. 1994 Jun;5(3):193-9. doi: 10.1006/scel.1994.1024.
The dynamic behavior of pure actin in vitro is more complex than that of most simple polymers, due to the energy input from the irreversible nucleotide hydrolysis associated with polymerization. However, the dynamic behavior of actin is vastly more complicated inside cells, where dozens of different types of actin-binding proteins alter every rate constant for actin polymerization and the chemical environment is inhomogeneous both temporally and spatially. Actin dynamics in cells are tightly regulated, so that rapid filament polymerization can occur in response to external signals or at the front of an active lamellipodium, while rapid depolymerization occurs simultaneously elsewhere in the cell. Although more direct observations of actin dynamics in vivo are accumulating, it is not yet clear how to reconcile the behavior of actin in cells with its well-documented in vitro properties.
由于与聚合作用相关的不可逆核苷酸水解所输入的能量，体外纯肌动蛋白的动态行为比大多数简单聚合物更为复杂。然而，在细胞内，肌动蛋白的动态行为要复杂得多，数十种不同类型的肌动蛋白结合蛋白会改变肌动蛋白聚合作用的每个速率常数，并且化学环境在时间和空间上都是不均匀的。细胞中的肌动蛋白动力学受到严格调控，以便在响应外部信号时或在活跃的片状伪足前端能够发生快速的丝状体聚合，而在细胞的其他部位则同时发生快速解聚。尽管体内肌动蛋白动力学的直接观察结果越来越多，但目前尚不清楚如何将细胞中肌动蛋白的行为与其在体外已充分记录的特性相协调。
