Soil Ecology, RWTH Aachen, Aachen, Germany.
PLoS One. 2013 May 28;8(5):e64682. doi: 10.1371/journal.pone.0064682. Print 2013.
PTS(Ntr) is a regulatory phosphotransferase system in many bacteria. Mutation of the PTS(Ntr) enzymes causes pleiotropic growth phenotypes, dry colony morphology and a posttranslational inactivation of ABC transporters in Rhizobium leguminosarum 3841. The PTS(Ntr) proteins EI(Ntr) and 2 copies of EIIA(Ntr) have been described previously. Here we identify the intermediate phosphocarrier protein NPr and show its phosphorylation by EI(Ntr) in vitro. Furthermore we demonstrate that phosphorylation of EI(Ntr) and NPr is required for ABC transport activation and that the N-terminal GAF domain of EI(Ntr) is not required for autophosphorylation. Previous studies have shown that non-phosphorylated EIIA(Ntr) is able to modulate the transcriptional activation of the high affinity potassium transporter KdpABC. In R. leguminosarum 3841 kdpABC expression strictly depends on EIIA(Ntr). Here we demonstrate that under strong potassium limitation ABC transport is inactivated, presumably by non-phosphorylated EIIA(Ntr). This is to our knowledge the first report where PTS(Ntr) dictates an essential cellular function. This is achieved by the inverse regulation of two important ATP dependent transporter classes.
PTS(Ntr) 是许多细菌中的一种调节磷酸转移酶系统。PTS(Ntr) 酶的突变导致根瘤菌 3841 中多种生长表型、干燥菌落形态和 ABC 转运蛋白的翻译后失活。先前已经描述了 PTS(Ntr) 蛋白 EI(Ntr)和 2 个拷贝的 EIIA(Ntr)。在这里，我们鉴定了中间磷酸载体蛋白 NPr，并在体外显示其被 EI(Ntr)磷酸化。此外，我们证明 EI(Ntr)和 NPr 的磷酸化是 ABC 转运激活所必需的，并且 EI(Ntr)的 N 端 GAF 结构域不是自身磷酸化所必需的。先前的研究表明，非磷酸化的 EIIA(Ntr)能够调节高亲和力钾转运蛋白 KdpABC 的转录激活。在根瘤菌 3841 中，kdpABC 的表达严格依赖于 EIIA(Ntr)。在这里，我们证明在强钾限制下，ABC 转运被失活，可能是由于非磷酸化的 EIIA(Ntr)。据我们所知，这是第一个报告 PTS(Ntr)决定重要细胞功能的报告。这是通过两种重要的 ATP 依赖性转运蛋白类别的反向调节来实现的。
