【摘要】 CsrA(在有些细菌例如十字花科黒腐病菌中也称为RsmA,统称CsrA/RsmA)是一类在细菌中广泛分布而且氨基酸序列非常保守的RNA结合蛋白。研究表明,CsrA/RsmA作为转录后全局调控因子参与了包括细胞碳代谢、次生代谢、运动性、生物被膜形成以及动植物病原菌的致病过程等许多细胞过程的调控。CsrA/RsmA在不同的细菌中的生物学功能各有异同。在大肠杆菌中,CsrA的主要功能是控制细胞的碳代谢、运动性和生物被膜形成;而在十字花科黑腐病菌(Xanthomonas campestris pathovar campestris,Xcc)中,CsrA的同源蛋白RsmA的主要功能除了控制碳代谢、运动性和生物被膜形成外,还控制致病性和胞外酶的产生。大肠杆菌的CsrA(CsrAE.coli)是否具有XccRsmA(RsmAXcc)的功能?为了回答这个问题,我们用大肠杆菌的csrA基因(csrAE.coli)互补Xcc的rsmA基因(rsmAXcc)的缺失突变体DM2506。结果显示,csrAE.coli能够互补DM2506的所有表型,说明CsrAE.coli具有RsmAXcc的全部功能。更重要的是,我们发现,无论是rsmAXcc突变体还是野生型菌株,导入表达CsrAE.coli的质粒后均导致其致胞外蛋白酶活性的严重下降,证明CsrAE.coli具有抑制Xcc胞外蛋白酶活性的作用。进一步的实验证实,CsrAE.coli的C末端第53～61位氨基酸残基具有抑制Xcc胞外蛋白酶活性的功能。更多还原

【Abstract】 CsrAs(also known as RsmA in some bacteria such as Xanthomonas campestris pathovar campestris(Xcc);collectively known as CsrAs/RsmA) are a family of widely distributed and highly conserved RNA-binding proteins in various bacterial species.It has been shown that CsrAs/RsmAs acting as post-transcriptional global regulators play important roles in the regulation of various cellular processes including carbon metabolism,secondary metabolism,cell motility,biofilm formation as well as the pathogenesis of plant and animal bacterial pathogens.CsrAs/RsmAs have both common and different biological functions in different bacteria.In E.coli,the major role of CsrA is controlling carbon metabolism,cell motility and biofilm formation,while in Xcc,in addition to roles described above,RsmA also plays important roles in the regulation of extracellular emzyme activity and virulence.In this study,we used the csrA gene of E.coli(csrAE.coli) to complement the rsmA deletion mutant of Xcc(rsmAXcc) to find out whether E.coli CsrA(CsrAE.coli) has the same functions as Xcc RsmA(RsmAXcc).Our results showed that csrAE.coli can completely complement the phenotypes of rsmAXcc mutant,demonstrating that CsrAE.coli has the same function as RsmAXcc.More interestingly,we found that introducing a plasmid expressing CsrAE.coli into either the wild type strain or the rsmAXcc mutant resulted in great reduction in their extracellular protease activities,indicating that CsrAE.coli has the ability to inhibit the extracellular protease activity of Xcc.Further experiments demonstrated that amino acid residues at position 53 to 61 from the C-terminus end of E.coli CsrA have the inhibition function.更多还原