Department of Physics, Simon Fraser University, Burnaby, BC, Canada V5A1S6.
Department of Physics, Simon Fraser University, Burnaby, BC, Canada V5A1S6
Proc Natl Acad Sci U S A. 2017 Oct 17;114(42):11057-11062. doi: 10.1073/pnas.1707534114. Epub 2017 Oct 3.
Biomolecular machines consume free energy to break symmetry and make directed progress. Nonequilibrium ATP concentrations are the typical free energy source, with one cycle of a molecular machine consuming a certain number of ATP, providing a fixed free energy budget. Since evolution is expected to favor rapid-turnover machines that operate efficiently, we investigate how this free energy budget can be allocated to maximize flux. Unconstrained optimization eliminates intermediate metastable states, indicating that flux is enhanced in molecular machines with fewer states. When maintaining a set number of states, we show that-in contrast to previous findings-the flux-maximizing allocation of dissipation is not even. This result is consistent with the coexistence of both "irreversible" and reversible transitions in molecular machine models that successfully describe experimental data, which suggests that, in evolved machines, different transitions differ significantly in their dissipation.
生物分子机器利用自由能打破对称并进行定向运动。非平衡态的 ATP 浓度是典型的自由能来源，分子机器的一个循环消耗一定数量的 ATP，提供固定的自由能预算。由于进化应该有利于快速转换、高效运作的机器，我们研究如何分配这个自由能预算以最大化通量。无约束优化消除了中间亚稳态，表明具有较少状态的分子机器可以增强通量。当维持一定数量的状态时，我们表明——与之前的发现相反——耗散的最大通量分配并非均匀的。这一结果与成功描述实验数据的分子机器模型中同时存在“不可逆”和可逆跃迁相一致，这表明在进化的机器中，不同的跃迁在耗散方面有显著差异。
