Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama-shi, Saitama-ken 338-8570, Japan.
Biochem Biophys Res Commun. 2012 May 4;421(2):296-300. doi: 10.1016/j.bbrc.2012.04.003. Epub 2012 Apr 7.
The pgsA gene encodes the enzyme for the committed step in the synthesis of acidic phospholipids in Escherichia coli, and the pssA gene does the same for zwitterionic phospholipid. It has been reported that the Rcs and Cpx phosphorelay signal transduction systems are activated in pgsA- and pssA-defective mutants, respectively. In this study, we show that the Cpx system is activated also in a pgsA mutant, whereas the Rcs system was not activated in a pssA mutant. Lack of phosphatidylglycerol in pgsA mutants causes inadequate modification of lipoproteins, resulting in poor localization to the outer membrane. The outer membrane lipoprotein RcsF is necessary for the response of the Rcs system to various stimuli, and Rcs activation in pgsA mutants involves inner membrane mislocalization of this lipoprotein. The outer membrane lipoprotein NlpE, however, while necessary for the surface adhesion-induced Cpx response, was not involved in Cpx activation in the pgsA mutant.
pgsA 基因编码大肠杆菌酸性磷脂合成中确定步骤的酶，而 pssA 基因则编码两性离子磷脂的相同酶。据报道，Rcs 和 Cpx 磷酸传递信号转导系统分别在 pgsA 和 pssA 缺陷突变体中被激活。在本研究中，我们表明 Cpx 系统也在 pgsA 突变体中被激活，而 Rcs 系统在 pssA 突变体中未被激活。pgsA 突变体中缺乏磷脂酰甘油会导致脂蛋白修饰不足，从而导致其在外膜中的定位不良。外膜脂蛋白 RcsF 是 Rcs 系统对各种刺激作出反应所必需的，而 pgsA 突变体中 Rcs 的激活涉及到该脂蛋白在内膜中的错误定位。然而，外膜脂蛋白 NlpE 虽然是表面黏附诱导的 Cpx 反应所必需的，但它并不参与 pgsA 突变体中 Cpx 的激活。
