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使细胞适应环境变化的中心调节机制。在细菌中，磷酸化主要通过磷酸化组氨酸和天冬氨酸残基的双组分调节系统来完成。在过去的十年中，磷酸化的细菌蛋白的丝氨酸，苏氨酸和酪氨酸残基的真核细胞样蛋白激酶也被发现发挥了重要作用的信号。目前对细菌中类真核生物蛋白激酶的作用机制和信号通路知之甚少。我们在伤寒沙门氏菌（S.伤寒沙门氏菌（伤寒沙门氏菌），伤寒的病原体，一组基因，不存在于其他沙门氏菌血清型，其基因组已被测序。该基因簇由三个开放阅读框组成，编码与Ser/Thr蛋白激酶（prkX和prkY）和蛋白磷酸酶2C（prpZ）具有同源性的蛋白质。这三个功能相反的基因似乎控制着一个特异于S的信号通路。伤寒我们发现，这三个基因的缺失影响了S。巨噬细胞中的伤寒杆菌，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节和鉴定由这三种蛋白质可逆磷酸化的生理底物来更好地表征这种信号通路。这项拟议中的研究有可能提供第一个关于“真核生物样”磷酸化级联反应的详细图片，该级联反应可能与S。伤寒感染期间。

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.