Signal transduction by bacterial Ser/Thr kinases

由蛋白激酶和蛋白磷酸酶控制的可逆磷酸化是细胞适应环境变化的主要调控机制。在细菌中，磷酸化主要由组氨酸和天冬氨酸残基磷酸化的双组分调节系统完成。在过去的十年中，真核样蛋白激酶在丝氨酸、苏氨酸和酪氨酸残基上的细菌蛋白磷酸化也被发现在信号传导中起重要作用。真核样蛋白激酶在细菌中的作用机制和控制的信号通路尚不清楚。我们在伤寒病原体伤寒沙门氏菌血清型（S. Typhi）的基因组中发现了一组基因，这些基因在其他已测序的沙门氏菌血清型中不存在。该基因簇由三个开放阅读框组成，编码与丝氨酸/苏氨酸蛋白激酶（prkX和prkY）和蛋白磷酸酶2C （prpZ）同源的蛋白。这三个功能相反的基因似乎控制着伤寒沙门氏菌特有的信号通路。我们发现，这三个基因的缺失会影响伤寒沙门氏菌在巨噬细胞中的长期存活，表明这些基因与毒力有关。在这里，我们建议通过检查这三种蛋白质的酶活性以及它们通过共价修饰的调控，并确定被这三种蛋白质可逆磷酸化的生理底物，来更好地表征这一信号通路。拟议的研究有可能提供“真核样”磷酸化级联的第一张详细图片，该级联可能涉及伤寒沙门氏菌感染期间的长期持续。

Reversible phosphorylation controlled by protein kinases and protein phosphatases is a central regulatory mechanism that allows cells to adapt to environmental changes. In bacteria, phosphorylation is accomplished primarily by two-component regulatory systems that phosphorylate histidine and aspartate residues. In the last decade, phosphorylation of bacterial proteins on serine, threonine and tyrosine residues by eukaryotic-like protein kinases has also been found to play a major role in signaling. Little is known about the mechanism of action and signaling pathways controlled by eukaryotic-like protein kinases in bacteria. We identified in the genomes of Salmonella enterica serovar Typhi (S. Typhi), the etiologic agent of typhoid fever, a cluster of genes that is not present in other Salmonella serovars for which the genome has been sequenced. This gene cluster consists of three open reading frames encoding proteins with homology to Ser/Thr protein kinases (prkX and prkY) and protein phosphatase 2C (prpZ). These three genes of opposing functions appear to control a signaling pathway specific to S. Typhi. We showed that deletion of the three genes affects the long-term survival of S. Typhi in macrophages, indicating that these genes are involved in virulence. Here, we propose to better characterize this signaling pathway by examining the enzymatic activities of the three proteins as well as their regulation by covalent modification and identifying the physiological substrate(s) that is(are) reversibly phosphorylated by the three proteins. The proposed research has the potential to provide the first detailed picture of an "eukaryotic-like" phosphorylation cascade that could be involved in the long-term persistence of S. Typhi during infection.