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The Core Signaling Proteins of Bacterial Chemotaxis Assemble To Form an Ultrastable Complex

机译：细菌趋化性的核心信号蛋白组装形成超稳定复合物。

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摘要

The chemosensory pathway of bacterial chemotaxis forms a polar signaling cluster in which thenfundamental signaling units, the ternary complexes, are arrayed in a highly cooperative, repeating lattice. Thenrepeating ternary units are composed of transmembrane receptors, histidine-kinase CheA, and couplingnprotein CheW, but it is unknown how these three core proteins are interwoven in the assembled ultrasensitivenlattice. Here, to further probe the nature of the lattice, we investigate its stability. The findings reveal that oncenthe signaling cluster is assembled, CheA remains associated and active for days in vitro. All three corencomponents are required for this ultrastable CheA binding and for receptor-controlled kinase activity. Thenstability is disrupted by low ionic strength or high pH, providing strong evidence that electrostatic repulsionnbetween the highly acidic core components can lead to disassembly. We propose that ultrastability arisesnfrom the assembled lattice structure that establishes multiple linkages between the core components,nthereby conferring thermodynamic or kinetic ultrastability to the bound state. An important, knownnfunction of the lattice structure is to facilitate receptor cooperativity, which in turn enhances pathwaynsensitivity. In the cell, however, the ultrastability of the lattice could lead to uncontrolled growth of thensignaling complex until it fills the inner membrane. We hypothesize that such uncontrolled growth isnprevented by an unidentified intracellular disassembly system that is lost when complexes are isolated fromncells, thereby unmasking the intrinsic complex ultrastability. Possible biological functions of ultrastability arendiscussed.
机译：细菌趋化性的化学感应途径形成一个极性信号簇，然后基本的信号单元（三元复合物）排列在高度协作的重复晶格中。然后重复的三元单元由跨膜受体，组氨酸激酶CheA和偶联蛋白CheW组成，但是尚不知道这三种核心蛋白是如何在组装的超敏感晶格中交织的。在这里，为了进一步探究晶格的性质，我们研究了其稳定性。这些发现表明，Oncenthe信号簇已组装好，CheA在体外仍保持关联并活跃数天。超稳定的CheA结合和受体控制的激酶活性均需要所有三个核心组分。然后低离子强度或高pH破坏了稳定性，提供了有力的证据表明高酸性核心成分之间的静电排斥会导致分解。我们认为，超稳定是由组装的晶格结构引起的，该结构在核心组件之间建立了多个连接，从而赋予键合态热力学或动力学超稳定性。晶格结构的一个重要的已知功能是促进受体的协同作用，继而增强通路的敏感性。然而，在电池中，晶格的超稳定性可能导致信号复合物的不可控生长，直到其填满内膜。我们假设这样的不受控制的生长是由无法识别的细胞内拆卸系统所预防的，当从ncells中分离出复合物时，该系统会丢失，从而掩盖了固有的复合物超稳定性。没有讨论超稳定的可能生物学功能。

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  • 来源
    《Biochemistry》 |2009年第29期|p.6975-6987|共13页
  • 作者

    Annette H. Erbse and Joseph J. Falke;

  • 作者单位

    Department of Chemistry, and Biochemistry and Molecular Biophysics Program, University of Colorado,Boulder, Colorado 80309-0215;

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