Four-helical-bundle structure of the cytoplasmic domain of a serine chemotaxis receptor
Four-helical-bundle structure of the cytoplasmic domain of a serine chemotaxis receptor
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作者：
Kim, KK;Yokota, H;Kim, SH
细菌趋化性受体是具有简单信号传导途径的跨膜受体，其中包含与跨膜信号识别和转导、信号如何在途径中的分子之间传递以及如何实现对持续信号的适应的一般理解相关的元素(1)。与许多在配体结合时通过寡聚化发出信号的哺乳动物受体相反(2)，趋化性受体即使在不存在配体的情况下也是二聚体，并且它们的信号传导不依赖于单体-二聚体平衡(3)。细菌趋化受体由配体结合域、由两个螺旋TM1和TM2组成的跨膜域以及胞质域组成。所有已知的细菌趋化性受体都具有高度保守的胞质结构域，它将来自不同配体结构域的信号联合成通往鞭毛马达的单一信号传导途径。在这里，我们报道了大肠杆菌丝氨酸趋化性受体胞质结构域的晶体结构，该结构揭示了一个 200 埃长的卷曲螺旋，由两个通过“U 形转弯”连接的反向平行螺旋组成。其中两个结构域在受体的细胞质部分形成长的、超螺旋的四螺旋束。
The bacterial chemotaxis receptors are transmembrane receptors with a simple signalling pathway which has elements relevant to the general understanding of signal recognition and transduction across membranes, how signals are relayed between molecules in a pathway, and how adaptation to a persistent signal is achieved(1). In contrast to many mammalian receptors which signal by oligomerizing upon ligand binding(2), the chemotaxis receptors are dimeric even in the absence of their ligands, and their signalling does not depend on a monomer-dimer equilibrium(3). Bacterial chemotaxis receptors are composed of a ligand-binding domain, a transmembrane domain consisting of two helices TM1 and TM2, and a cytoplasmic domain. All known bacterial chemotaxis receptors have a highly conserved cytoplasmic domain, which unites signals from different ligand domains into a single signalling pathway to flagella motors. Here we report the crystal structure of the cytoplasmic domain of a serine chemotaxis receptor of Escherichia coli, which reveals a 200 Angstrom-long coiled-coil of two antiparallel helices connected by a 'U-turn'. Two of these domains form a long, supercoiled, four-helical bundle in the cytoplasmic portion of the receptor.