Department of Molecular Biology and Biotechnology, The Krebs Institute, University of Sheffield, Sheffield S10 2TN, UK.
Open Biol. 2013 Jun 5;3(6):130046. doi: 10.1098/rsob.130046.
Complex 3'-5'-cyclic diguanylic acid (c-di-GMP) responsive regulatory networks that are modulated by the action of multiple diguanylate cyclases (DGC; GGDEF domain proteins) and phosphodiesterases (PDE; EAL domain proteins) have evolved in many bacteria. YfgF proteins possess a membrane-anchoring domain (MASE1), a catalytically inactive GGDEF domain and a catalytically active EAL domain. Here, sustained expression of the Salmonella enterica spp. Enterica ser. Enteritidis YfgF protein is shown to mediate inhibition of the formation of the aspartate chemotactic ring on motility agar under aerobic conditions. This phenomenon was c-di-GMP-independent because it occurred in a Salmonella strain that lacked the ability to synthesize c-di-GMP and also when PDE activity was abolished by site-directed mutagenesis of the EAL domain. YfgF-mediated inhibition of aspartate chemotactic ring formation was impaired in the altered redox environment generated by exogenous p-benzoquinone. This ability of YfgF to inhibit the response to aspartate required a motif, (213)Lys-Lys-Glu(215), in the predicted cytoplasmic loop between trans-membrane regions 5 and 6 of the MASE1 domain. Thus, for the first time the function of a MASE1 domain as a redox-responsive regulator of bacterial responses to aspartate has been shown.
在许多细菌中，进化出了复杂的 3'-5'-环二鸟苷酸（c-di-GMP）反应性调控网络，该网络受多种二鸟苷酸环化酶（DGC；GGDEF 结构域蛋白）和磷酸二酯酶（PDE；EAL 结构域蛋白）的作用调控。YfgF 蛋白具有膜锚定结构域（MASE1）、无催化活性的 GGDEF 结构域和具有催化活性的 EAL 结构域。本研究表明，肠炎沙门氏菌 YfgF 蛋白的持续表达可介导有氧条件下在运动琼脂上抑制天冬氨酸趋化环的形成。这种现象与 c-di-GMP 无关，因为它发生在缺乏合成 c-di-GMP 能力的沙门氏菌菌株中，并且当通过 EAL 结构域的定点突变消除 PDE 活性时也会发生。在由外源对苯醌产生的改变的氧化还原环境中，YfgF 介导的天冬氨酸趋化环形成抑制受损。YfgF 抑制天冬氨酸反应的能力需要 MASE1 结构域跨膜区域 5 和 6 之间预测的细胞质环中的一个基序（213）Lys-Lys-Glu(215)。因此，首次表明 MASE1 结构域作为细菌对天冬氨酸反应的氧化还原响应调节剂的功能。
