Identification and Characterization of the Nuclease Activity of the Extracellular Proteins from Salmonella enterica Sero
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Identification and Characterization of the Nuclease Activity of the Extracellular Proteins from Salmonella enterica Serovar Typhimurium Chengshui Liao1 · Mengke Zhang1 · Xiangchao Cheng1,2 · Qi Li1 · Fuchao Mao1 · Xiaoli Wang3 · Chuan Yu1 · Zuhua Yu1 · Yanyan Jia1 · Jing Li1 · Lei He1 · Chunjie Zhang1 · Yinju Li1 · Tingcai Wu1 Received: 22 April 2020 / Accepted: 3 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Pathogens have evolved an array of strategies to establish a productive infection. The extracellular proteins secreted by pathogens are one of unique mechanisms to evade the host innate immune response. Many secretory proteins transported by the bacterial secretion systems have been widely investigated in Salmonella. Certain extracellular nucleases are essential for bacterial pathogenesis. However, there is no current data available for the enzymatic properties of the proteins secreted by Salmonella. Therefore, in the present study we have identified and characterized the nuclease activity of the extracellular proteins from Salmonella enterica serovar Typhimurium. It was demonstrated that the extracellular proteins from S. Typhimurium exhibited the deoxyribonucleases activity against λDNA by agarose gel electrophoresis and agar plate diffusion method. The activity was observed at 16 °C, 37 °C and 42 °C, and found to be highest at 42 °C and inhibited at temperatures over 60 °C. The nuclease activity was stable under alkaline conditions (pH 7–10) and the optimum pH was 9.0. The nuclease activity was promoted at high ionic strength of Ba2+, Ca2+, Mg2+, and Ni2+. Nuclease zymography analysis revealed that there were four activity bands in the extracellular proteins; followed by LC-ESI/MS/MS analysis seven proteins were identified. As demonstrated by nuclease zymography, the recombinant 5′-nucleotidase protein expressed in the prokaryotic expression system displayed the DNase activity. To our knowledge, the present findings represent the first direct and unambiguous demonstration of the nuclease activity of the extracellular proteins from S. Typhimurium, and it provides an important fundamental for further investigation of the role of the extracellular proteins in pathogenicity and immune evasion. Abbreviations T3SSs Type III secretion systems SPIs Salmonella Pathogenicity islands SCV Salmonella-Containing vacuole NETs Neutrophil extracellular traps * Chengshui Liao [email protected] * Xiangchao Cheng [email protected] 1
College of Animal Science and Technology /Luoyang Key Laboratory of Live Carrier Biomaterial and Animal Disease Prevention and Control, Henan University of Science and Technology, 263 Kaiyuan Road, Luoyang 471023, People’s Republic of China
2
Luoyang Vocational and Technical College, Luoyang 471099, People’s Republic of China
3
Medical College, Henan University of Science and Technology, Luoyang 471023, People’s Republic of China
SDS Sodium dodecyl sulfate BCA Bicinchoninic acid IPTG Isopropyl ß-d-1-thiogalactoside TEM
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