Study On Soluble Protein Complexes In Shigella Flexneri

Shigella flexneri is the most common pathogen causing bacillary dysentery, has a high degree of homology and similarity at the genomic level with E. coli. The main difference between the two spieces lies in the presence or absence of the virulence plasmid. At the same time, Shigella spp. is a typical example of gene coevolution and mutual adaptation between plasmid virulence genes and chromosomal virulence genes. A protein is not independent to complete a biological function, but in formation of protein complexes and regulation with other proteins. Only single protein qualitative and functional analysis can not meet the demand from the overall level of understanding of Shigella. Therefore, we planned to analyze Shigella soluble protein complex to futher reveal the physiological characteristic,53homomultimeric protein complexes and nine heteromultimeric protein complexes from S. flexneri2a strain2457T were separated and identified. Among these,50homomultimeric protein complexes have been reported in E. coli, three potential homomultimeric protein complexes not described previously. And we wanted to know the reaction pathway of external environmental stimuli and the regulation mechanism in this organism.In the present study, the abundances of the protein complexes were compared following growth at37℃or30℃, and the abundances of three protein complexes (PyrB/PyrI, GlmS and MglB) related to the synthesis of lipopolysaccharides (LPS) appeared to be temperature-dependent. Many studies have shown that LPS is essential to the virulence of S. flexneri. Here, we reported the influence of temperature on the amount of LPS. At the same time, by comparing the differences of the abundances of the protein complexes between Shigella wild-type strain and virulence plasmid deletion mutant strain, E. coli wild-type strain and virulence plasmid import mutant strain, we found that S. flexneri virulence plasmid altered the acid resistance of the strain, by regulating the expression of glutamic acid decarboxylase and ATP synthase. As an intestinal pathogen, acid resistance is very important phenotype for Shigella spp. to survive gastric acid and intestinal volatile fatty acids. It is considered that strong acid resistance might be attributing to ultra-low infection dose of Shigella bacteria, and this study would give more details for the specific acid resistance mechanism of S.flexneri.In summary, construction of S. flexneri soluble protein complex profiles, extend the understanding of the physiological characteristics of S. flexneri, and discovering of abundance change of protein complexes between the two different culture temperatures, provide a vital clue to comprehensive and in-depth analysis of Shigella pathogenic molecular mechanisms. In addition to the core virulence genes on the virulence plasmid, many genes on the chromosome are also involved in the pathogenesis of Shigella. To better study Shigella pathogenesis, we need to clarify the cross-talk between the virulence plasmid and the chromosome of this pathogen. Thus, we constructed the large virulence plasmid-deleteShigella mutant and the large virulence plasmid-imported E. coli mutant, respectively. Comparing the expression of these mutans and their parent strains opened a new idea of screening virulence-associated protein. The improvement of technology involved in this study has laid a solid foundation to the protein complexes analyses.