Inclán Yuki F, Vlamakis Hera C, Zusman David R
Graduate Group in Biophysics, University of California, Berkeley, CA, USA.
Mol Microbiol. 2007 Jul;65(1):90-102. doi: 10.1111/j.1365-2958.2007.05774.x.
Myxococcus xanthus utilizes two distinct motility systems for movement (gliding) on solid surfaces: adventurous motility (A-motility) and social motility (S-motility). Both systems are regulated by the Frz signal transduction pathway, which controls cell reversals required for directed motility and fruiting body formation. The Frz chemosensory system, unlike the Escherichia coli chemotaxis system, contains proteins with multiple response regulator domains: FrzE, a CheA-CheY hybrid protein, and FrzZ, a CheY-CheY hybrid protein. Previously, the CheY domain of FrzE was hypothesized to act as the response regulator output of the Frz system. In this study, using a genetic suppressor screen, we identified FrzZ and showed FrzZ is epistatic to FrzE, demonstrating that FrzZ is the principal output component of the pathway. We constructed M. xanthus point mutations in the phosphoaccepting aspartate residues of FrzZ and demonstrated the respective roles of these residues in group and single cell motility. We also performed in vitro assays and showed rapid phosphotransfer between the CheA domain of FrzE and each of the CheY domains of FrzZ. These experiments showed that FrzZ plays a direct role as an output of the Frz chemosensory pathway and that both CheY domains of FrzZ are functional.
黄色粘球菌利用两种不同的运动系统在固体表面移动（滑行）：冒险性运动（A 运动）和社会性运动（S 运动）。这两种系统都受 Frz 信号转导途径调控，该途径控制定向运动和子实体形成所需的细胞反转。与大肠杆菌趋化系统不同，Frz 化学感受系统包含具有多个应答调节结构域的蛋白质：FrzE，一种 CheA-CheY 杂合蛋白，以及 FrzZ，一种 CheY-CheY 杂合蛋白。此前，有人推测 FrzE 的 CheY 结构域作为 Frz 系统的应答调节输出。在本研究中，我们通过遗传抑制筛选鉴定出 FrzZ，并表明 FrzZ 对 FrzE 呈上位性，证明 FrzZ 是该途径的主要输出成分。我们构建了 FrzZ 磷酸化接受天冬氨酸残基的黄色粘球菌点突变体，并证明了这些残基在群体和单细胞运动中的各自作用。我们还进行了体外试验，结果表明 FrzE 的 CheA 结构域与 FrzZ 的每个 CheY 结构域之间能快速进行磷酸转移。这些实验表明，FrzZ 作为 Frz 化学感受途径的输出发挥直接作用，并且 FrzZ 的两个 CheY 结构域均具有功能。
