Phosphoproteomic Analysis of Spiroplasma eriocheiris and Crosstalk with Acetylome Reveals the Role of Post-Translational Modifications in Metabolism

Abstract

Background: Post-translational modifications (PTMs) such as phosphorylation are an essential regulatory mechanism of protein function and associated with a range of biological processes beyond genome and transcriptome. Spiroplasma eriocheiris, a wall-less helical bacterium, is one of the smallest known self-replicating bacteria and a novel pathogen of freshwater crustacean. Methods: To study the physiological characteristics and regulatory mechanism of S. eriocheiris, the protein phosphorylation in the bacterium were systematically investigated by iTRAQ analyzed by LC-MS/MS. Data are available via ProteomeXchange with identifier PXD015055. Results: We identified 465 phosphorylation sites in 246 proteins involved in a broad spectrum of fundamental biological process ranging from regulation of metabolic pathways to protein synthesis. Notably, most proteins in glycolysis and all proteins in the arginine deiminase system were phosphorylated. Meanwhile, the cytoskeleton proteins (Fibril, Mrebs and ET-Tu) were all phosphorylated suggest that the phosphorylation also may play a crucial role in cell skeleton formation. We have got a lot of highly conserved proteins and phosphorylation sites by analysis, and those proteins or phosphorylation sites were mainly participated in glucose metabolism and protein synthesis. Crosstalk analysis with protein-protein interaction networks in relation to phosphorylated proteins and acetylated proteins found that the two PTMs are required for playing crucial roles in many physiological processes in S. eriocheiris. By comparing the relative positions of acetylation versus phosphorylation, we found that the two modifications often found close to proximity on the same protein. Conclusions: The results imply that there is previously unreported hidden role of phosphorylation that define the functional state of Spiroplasma.