Screening Of Traditional Chinese Medicines Against Streptococcus Suis By CysM Target Protein

Streptococcus suis is the most vital swine pathogen,an emerging zoonotic agent that cause several infections such as meningitis,endocarditis,and septicaemia followed by deafness in humans and pig industries worldwide.In recent years the study showed the development of resistance in S.suis against certain antibiotics,thus increases the risk for therapeutic failure in both animals and humans.Several studies have shown that CysM,a key enzyme in cysteine biosynthesis in certain bacteria include Streptococcus suis(S.suis)considered as a possible target for the development of antibacterial agents,for which there are currently a limited number of biological targets.The inhibition of CysM protein for producing cysteine is considered a good measure to prevent bacterial resistance and survival.Traditional Chinese medicines(TCMs)have played a significant role in the history of recent research medicine.Therefore,discovering the Antibacterial effect of TCMs in Streptococcus suis might be an important way to solve the problem of prevention,control,and treatment of Streptococcus suis.In this study,we used homology modeling to generate the 3D structure of CysM protein using the MODELLER4.0 program.The PROCHECK,ERRAT,and VERFY were used to evaluate the model structural quality.XP docking was done by Maestro 10.6 in Schr(?)dinger Suite.Twenty hits screened drugs from the docking study were used in vitro to identify the potential antibacterial effect of each drug on Streptococcus suis(S.suis).The specific research results are as follows:(1)Homology modeling and MODELLER 4.0 program provided a 3D structure model of CysM receptor.(2)The PROCHECK,ERRAT,and VERFY were used to evaluate the model structural quality which showed 92.5% residues in favorable regions,the predicted total quality factor of the three-level model of CysM domain was 93.5 and The Verify-3D results of CysM showed that100% of the amino acids scored in the 3D/1D profile were ≥ 0.2.(3)Twenty kinds of TCMs monomers with high affinity to binding with CysM were identified by the Molecular docking study.Such as Chlorogenic acid,D-Trehalose,Aesculin,Phlorizin,Fraxoside,Sodium Danshensu,Danshensu,Melatonin,Bengenin,Aucubin,Gastrodin,Gallic acid,Shikimic Acid,Helicid,Inosine,5-hydroxytryptophan,Ellagic acid,Cordycepin,Theophylline acetate,Honokiol.Gallic acid interaction amino acids with CysM are Lys44,Ser266,Gly178,Thr179,and Gly180 and docking energy-11.833 kcal/mol.(4)In vitro antibacterial effect of TCMs on Streptococcus suis test showed that: i)In wild strain,Except,chlorogenic acid MIC was 886.5 μg/ml,Danshensu MIC was 128 μg/ml,bergenin MIC was 1642 μg/ml,Gallic acid MIC was 212.5 μg/ml,cordycepin MIC was 628 μg/ml showed antibacterial effects,the other Chinese medicines had no antibacterial effect on Streptococcus suis standard strain.ii)With tylosin antibiotic,except chlorogenic acid MIC was 1773 μg/ml,Danshensu MIC was 128 μg/ml,Danshensu Sodium MIC was 128 μg/ml,Gallic acid MIC was 425μg/ml,Cordycepin MIC was 628 μg/ml,the other TCMs had no antibacterial effect on tylosin induced on Streptococcus suis strain.iii)With CysM mutant,Except,chlorogenic acid MIC was887 μg/ml,Danshensu MIC was 128 μg/ml,Danshensu Sodium MIC was 128 μg/ml,Gallic acid MIC was 106 μg/ml,Cordycepin MIC was 1,256 μg/ml,honokiol MIC was 128 μg/ml had the antibacterial effect,the other TCMs had no antibacterial effect on CysM knockout of Streptococcus suis strain.In summary,the Molecular docking study was used to predict the potential inhibitors of CysM protein for the first time in this study.It was found that certain TCMs have antibacterial effects on Streptococcus suis in vitro,however,Gallic acid has shown the best inhibitory effect compared with other five TCMs which laid a theoretical foundation for the research and development of antibacterial effect of TCMs in Streptococcus suis.