ABSTRACT
Type Ⅶ secretion system(T7SS) is a novel and specialized secretion system discovered in recent years. It was first found in Mycobacterium tuberculosis. Type Ⅶ secretion system is involved in the secretion of virulence-associated proteins, the interaction between pathogens and hosts and the balance of zinc/iron ions. Moreover,it plays a critical role in the growth and pathogenesis of Mycobacteria. This review summarizes the components,substrates and translocation mechanisms of the type Ⅶ secretion system and its relation to the virulence of Mycobacteria aiming to provide references for developing novel strategies for disea-ses diagnosis,treatment and prevention.
ABSTRACT
Objective To study the mechanism of two-component system of MprAB and TrcRS in synergistically regulating gene rv1057 expression of Mycobacterium tuberculosis.Methods The in vivo specific binding capability of MprA and TrcR with the target gene promoter region was analyzed using electrophoretic mobility shift assay.The transcription level of target gene was analyzed by using fluorescence quantitative polymerase chain reaction,and all results were compared with the fold changes in H37Rv strain plus SDS group,which was set as one unit.The expression level of target gene was analyzed by using western blot;the transcription ability of different promoter region of rv1057 was detected through lacZ report gene.The t test was used for statistical analysis.Results MprA was able to bind to trcR promoter.The expressions of trcR in D981 and H37Rv strains without SDS were 1.7 and 2.5 folds of the expression of H37Rv strains with SDS groups,respectively.The difference between these two groups was statistically significant (t=18.54,P＜0.05).With SDS,the expressions of trcR in D981 and H37Rv strains were 1.0 and 2.1 folds of the expression of H37Rv strains plus SDS group,respectively.The expressions of trcR in D981 and H37Rv strains were significantly different (t=15.86,P＜0.05).After adding SDS during the culture of H37Rv strains,the expression of trcR in H37Rv decreased.The difference between these two groups was statistically significant (t=16.99,P＜0.05).Both MprA and TrcR were able to bind to rv1057 promoter and regulate its expression.MprA activated the expression of rv1057,while TrcR repressed the expression of rv1057.Conclusions MprAB and TrcRS synergistically regulate the expression of rv1057.MprA is activated in the presence of SDS,which represses the transcription of trcR and activates the transcription of rv1057.However,TrcR represses the transcription of rv1057 in the absence of SDS.