Abstract
Streptococcus suis is an important pathogen in pigs and can also cause severe infections in humans. However, little is known about proteins associated with cell growth and pathogenicity of S. suis. In this study, a guanosine triphosphatase (GTPase) MnmE homolog was identified in a Chinese isolate (SC19) that drives a tRNA modification reaction. A mnmE deletion strain (ΔmnmE) and a complementation strain (CΔmnmE) were constructed to systematically decode the characteristics and functions of MnmE both in vitro and in vivo studies via proteomic analysis. Phenotypic analysis revealed that the ΔmnmE strain displayed deficient growth, attenuated pathogenicity, and perturbation of the arginine metabolic pathway mediated by the arginine deiminase system (ADS). Consistently, tandem mass tag -based quantitative proteomics analysis confirmed that 365 proteins were differentially expressed (174 up- and 191 down-regulated) between strains ΔmnmE and SC19. Many proteins associated with DNA replication, cell division, and virulence were down-regulated. Particularly, the core enzymes of the ADS were significantly down-regulated in strain ΔmnmE. These data also provide putative molecular mechanisms for MnmE in cell growth and survival in an acidic environment. Therefore, we propose that MnmE, by its function as a central tRNA-modifying GTPase, is essential for cell growth, pathogenicity, as well as arginine metabolism of S. suis.
Highlights
Streptococcus suis is an important zoonotic pathogen that causes a wide range of diseases, including meningitis, arthritis, pneumonia, and septicemia (Goyette-Desjardins et al, 2014)
MnmE is an evolutionarily conserved tRNA-modifying enzyme that contributes to correct interactions between codons and anticodons during translation in both eukaryotic and prokaryotic cells (Fislage et al, 2014)
In E. coli, MnmE is relevant to cell growth, and mutations are lethal in specific strains (Martinez-Vicente et al, 2005)
Summary
Streptococcus suis is an important zoonotic pathogen that causes a wide range of diseases, including meningitis, arthritis, pneumonia, and septicemia (Goyette-Desjardins et al, 2014). More than 20 virulence-associated factors responsible for the pathogenicity of S. suis have been identified over the past four decades, which include suilysin, muramidase-released protein, twocomponent signal transduction systems, extracellular factors, fibronectin- and fibrinogen-binding proteins (FBPs), enolase, the arginine deiminase system (ADS), and glyceraldehyde-3phosphate dehydrogenase (Jing et al, 2008; Feng et al, 2014; Fulde et al, 2014; Tan et al, 2017; Zhong et al, 2018). S. suis must adapt metabolically to survive in vivo and maintain pathogenesis (Willenborg et al, 2016). During this process, many proteins are either up- or down-regulated at the translation level in response to environmental stimuli and change (Gao et al, 2016). The underlying mechanisms of preferential regulation of proteins by S. suis during specific steps of host infection have not been clearly demonstrated
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