Proteomics Analysis Of A PurR Super-repressing Mutant Of Salmonella Typhimurium

By using a purR super-repressing mutant of S.typhimurim,strain 5-28,this thesis concentrated on studying(1) the protein expression profile of strain 5-28 under lactose selective condition;(2) the protein basis related to purR super-repression phenotype via proteomic analysis.The results were showed as following.(1) When the soluble cellular proteins expressed by strain 5-28 incubated under lactose selective condition for 24 hours were compared with those expressed in cells incubated in LB,nineteen different protein spots were observed.Twelve of them were further analyzed by MALDI-TOF MS and 8 kinds of protein were identified.Among them,five proteins were up-regulated,including maltoporin(LamB),periplasmic maltose-binding protein(MalE),D-galactose-binding periplasmic protein precursor (MglB),putative alcohol dehydrogenase and chorismate synthase;three proteins were down-regulated,including Succinate dehydrogenase catalytic subunit,phase 1 flagellin and aspartate ammonia-lyase.Based on these results,we speculated that the expression of proteins were regulated byσ~s,cAMP:CRP orσ~E under lactose selective condition,and were in favor of bacteria survival during periods of nutrient starvation.(2) Comparison of the soluble cellular proteins expressed by strain 5-28 with those expressed by its original strain TT12306,five different protein spots were observed. All these proteins were analyzed by MALDI-TOF MS.In strain 5-28,the expression of serine hydroxymethyltransferase was increased by 2.3-fold,whereas the expression of other four proteins,glycerophosphoryl diester phosphodiesterase periplasmic precursor,OmpW,OmpA and Fumarate hydratase were decreased by 3.2-fold,22.7-fold, 4-fold and 11.8-fold,respectively.The roles of these proteins in the occurrence of purR super-repression need further investigation.