Das Rahul Kumar, Kolomeisky Anatoly B
Department of Chemistry, Rice University, Houston, Texas 77005, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Jun;77(6 Pt 1):061912. doi: 10.1103/PhysRevE.77.061912. Epub 2008 Jun 17.
Motor proteins are active enzyme molecules that play a crucial role in many biological processes. They transform chemical energy into mechanical work and move unidirectionally along rigid cytoskeleton filaments. Single-molecule experiments indicate that motor proteins, consisting of two motor domains, move in a hand-over-hand mechanism where each subunit changes between trailing and leading positions in alternating steps, and it is assumed that these subunits do not interact with each other. However, recent experiments on heterodimeric kinesins suggest that the motion of motor domains is not independent, but rather strongly coupled and coordinated, although the mechanism of these interactions is not known. We propose a simple discrete stochastic model to describe the dynamics of homodimeric and heterodimeric two-headed motor proteins. It is argued that interactions between motor domains modify original free energy landscapes for each motor subunit, while motor proteins still move via the hand-over-hand mechanism but with different transition rates specified by the new free energy profiles. Our calculations of biophysical properties agree with experimental observations. Several ways to test the theoretical model are proposed.
马达蛋白是活性酶分子，在许多生物过程中发挥着关键作用。它们将化学能转化为机械功，并沿着刚性细胞骨架丝单向移动。单分子实验表明，由两个马达结构域组成的马达蛋白以交替式机制移动，其中每个亚基在交替步骤中在拖尾和领先位置之间变化，并且假定这些亚基彼此不相互作用。然而，最近对异源二聚体驱动蛋白的实验表明，马达结构域的运动并非独立，而是强烈耦合和协调的，尽管这些相互作用的机制尚不清楚。我们提出了一个简单的离散随机模型来描述同型二聚体和异型二聚体双头马达蛋白的动力学。有人认为，马达结构域之间的相互作用改变了每个马达亚基的原始自由能景观，而马达蛋白仍通过交替式机制移动，但具有由新的自由能分布指定的不同转换速率。我们对生物物理性质的计算与实验观察结果一致。还提出了几种测试该理论模型的方法。
