Thormählen M, Marx A, Sack S, Mandelkow E
Max-Planck-Unit for Structural Molecular Biology, Notkestrasse 85, Hamburg, D-22603, Germany.
J Struct Biol. 1998;122(1-2):30-41. doi: 10.1006/jsbi.1998.3986.
Kinesin is a microtubule-dependent motor protein. We have recently determined the X-ray structure of monomeric and dimeric kinesin from rat brain. The dimer consists of two motor domains, held together by their alpha-helical neck domains forming a coiled coil. Here we analyze the nature of the interactions in the neck domain (residues 339-370). Overall, the neck helix shows a heptad repeat (abcdefg)n typical of coiled coils, with mostly nonpolar residues in positions a and d. However, the first segment (339-355) contains several nonclassical residues in the a and d positions which tend to weaken the hydrophobic interaction along the common interface. Instead, stabilization is achieved by a hydrophobic "coat" formed by the a and d residues and the long aliphatic moieties of lysines and glutamates, extending away from the coiled-coil core. By contrast, the second segment of the kinesin neck (356-370) shows a classical leucine zipper pattern in which most of the hydrophobic residues are buried at the highly symmetrical dimer interface. The end of the neck reveals the structure of a potential coiled-coil "trigger" sequence.
驱动蛋白是一种依赖微管的运动蛋白。我们最近确定了来自大鼠大脑的单体和二聚体驱动蛋白的X射线结构。二聚体由两个运动结构域组成，通过它们的α螺旋颈部结构域结合在一起，形成一个卷曲螺旋。在这里，我们分析了颈部结构域（残基339 - 370）中相互作用的性质。总体而言，颈部螺旋呈现出卷曲螺旋典型的七肽重复序列（abcdefg）n，a和d位置大多为非极性残基。然而，第一段（339 - 355）在a和d位置包含几个非经典残基，这些残基往往会削弱沿共同界面的疏水相互作用。相反，稳定作用是通过由a和d残基以及赖氨酸和谷氨酸的长脂肪族部分形成的疏水“外壳”实现的，该“外壳”从卷曲螺旋核心向外延伸。相比之下，驱动蛋白颈部的第二段（356 - 370）呈现出典型的亮氨酸拉链模式，其中大多数疏水残基埋藏在高度对称的二聚体界面处。颈部末端揭示了一个潜在的卷曲螺旋“触发”序列的结构。
