Drittes Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
J Mol Biol. 2012 Oct 19;423(2):159-68. doi: 10.1016/j.jmb.2012.06.043. Epub 2012 Jul 9.
Processive motility of individual molecules is essential for the function of many kinesin motors. Processivity for kinesins relies on communication between the two heads of a dimeric molecule, such that binding strictly alternates. The main communicating elements are believed to be the two neck linkers connecting the motors' stalks and heads. A proposed mechanism for coordination is the transmission of stress through the neck linkers. It is believed that the efficiency of gating depends on the length of the neck linker. Recent studies have presented support for a simple model in which the length of the neck linker directly controls the degree of processivity. Based on a previously published Kinesin-1/Kinesin-5 chimera, Eg5Kin, we have analyzed the motility of 12 motor constructs: we have varied the length of the neck linker in the range between 9 and 21 amino acids using the corresponding native Kinesin-5 sequence (Xenopus laevis Eg5). We found, surprisingly, that neither velocity nor force generation depended on neck-linker length. We also found that constructs with short neck linkers, down to 12 amino acids, were still highly processive, while processivity was lost at a length of 9 amino acids. Run lengths were maximal with neck linkers close to the native Kinesin-5 length and decreased beyond that length. This finding generally confirms the coordinating role of the neck linker for kinesin motility but challenges the simplest model postulating a motor-type-independent optimal length. Instead, our results suggest that different kinesins might be optimized for different neck-linker lengths.
单体的连续运动对于许多驱动蛋白的功能至关重要。驱动蛋白的连续性依赖于二聚体分子的两个头部之间的通讯，使得结合严格交替。主要的通讯元件被认为是连接马达茎和头部的两个颈部接头。协调的一个提出的机制是通过颈部接头传递应力。人们认为门控的效率取决于颈部接头的长度。最近的研究提出了一个简单的模型的支持，该模型认为颈部接头的长度直接控制连续性的程度。基于之前发表的 Kinesin-1/Kinesin-5 嵌合体 Eg5Kin，我们分析了 12 个马达结构的运动：我们使用相应的天然 Kinesin-5 序列（非洲爪蟾 Eg5）在 9 到 21 个氨基酸的范围内改变颈部接头的长度。令人惊讶的是，我们发现速度和力的产生都不依赖于颈部接头的长度。我们还发现，颈部接头短至 12 个氨基酸的构建体仍然具有很高的连续性，而当颈部接头的长度为 9 个氨基酸时，连续性就会丧失。颈部接头接近天然 Kinesin-5 长度时，运行长度最大，超过该长度后则会减小。这一发现普遍证实了颈部接头对驱动蛋白运动的协调作用，但挑战了最简单的模型，即假定一个与马达类型无关的最佳长度。相反，我们的结果表明，不同的驱动蛋白可能针对不同的颈部接头长度进行了优化。
