Theory and Biosystems, Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany.
J Chem Phys. 2010 Oct 21;133(15):155105. doi: 10.1063/1.3497001.
Actin polymerization is coupled to the hydrolysis of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and inorganic phosphate (P(i)). Therefore, each protomer within an actin filament can attain three different nucleotide states corresponding to bound ATP, ADP/P(i), and ADP. These protomer states form spatial patterns on the growing (or shrinking) filaments. Using Brownian dynamics simulations, the growth behavior of long filaments is studied, together with the associated protomer patterns, as a function of ATP-actin monomer concentration, C(T), within the surrounding solution. For concentrations close to the critical concentration C(T)=C(T,cr), the filaments undergo treadmilling, i.e., they grow at the barbed and shrink at the pointed end, which leads to directed translational motion of the whole filament. The corresponding nonequilibrium states are characterized by several global fluxes and by spatial density and flux profiles along the filaments. We focus on a certain set of transition rates as deduced from in vitro experiments and find that the associated treadmilling (or turnover) rate is about 0.08 monomers per second.
肌动蛋白聚合与三磷酸腺苷 (ATP) 水解成二磷酸腺苷 (ADP) 和无机磷酸 (P(i)) 相偶联。因此，肌动蛋白丝中的每个单体都可以达到与结合的 ATP、ADP/P(i) 和 ADP 对应的三种不同核苷酸状态。这些单体状态在生长（或收缩）的纤维上形成空间图案。使用布朗动力学模拟，研究了长纤维的生长行为以及与其相关的单体模式，作为周围溶液中 ATP-肌动蛋白单体浓度 C(T) 的函数。对于接近临界浓度 C(T)=C(T,cr) 的浓度，纤维经历踏车运动，即它们在珠状末端生长而在尖状末端收缩，这导致整个纤维的定向平移运动。相应的非平衡状态的特征是几个全局通量以及沿纤维的空间密度和通量分布。我们关注从体外实验中推断出的一组特定的转换速率，并发现相关的踏车（或周转率）速率约为每秒 0.08 个单体。
