【摘要】 CsrA/RsmA蛋白家族是细菌中一类重要的转录后全局调控因子,它们调控细菌的碳代谢、次生代谢、运动、生物被膜形成以及致病等过程。CsrA/RsmA蛋白家族通常由60~72个氨基酸基组成,其中第1至第52位氨基酸高度保守,而第53位以后的氨基酸则高度可变。目前人们认为其氨基酸高度保守性是不同种属细菌CsrA/RsmA功能和作用机理相似的基础,但是其高度可变区与不同种属CsrA/RsmA蛋白功能差异的关系尚不清楚。我们之前的研究显示,大肠杆菌(Escherichia coli)的CsrA(CsrAE.coli)蛋白的高度可变区(第53至第61位氨基酸残基)具有强烈的抑制十字花科黒腐病菌(Xanthomonas campestris pathovar campestris,简称Xcc)胞外蛋白酶活性的能力。本研究中,我们采用丙氨酸置换方法,确定了CsrAE.coli可变区中抑制Xcc胞外蛋白酶活性必需的氨基酸残基。结果显示,CsrAE.coli蛋白的第54位赖氨酸(K54)、第60位丝氨酸(S60)和第61位酪氨酸(Y61)置换成丙氨酸后,CsrAE.coli蛋白丧失了抑制Xcc胞外蛋白酶活性的能力;而其它位点的丙氨酸置换不影响其抑制Xcc胞外蛋白酶活性的能力。这个结果证明K54、S60和Y61是CsrAE.coli抑制Xcc胞外蛋白酶活性所必需的,为揭示大肠杆菌的CsrAE.coli蛋白抑制Xcc胞外蛋白酶活性的分子机理奠定基础。更多还原

【Abstract】 Members of CsrA/RsmA family of proteins are important global regulators in bacteria, and they control carbon metabolism, secondary metabolism, motility, biofilm formation and pathogenesis at post-transcriptional level. CsrA/RsmA proteins are usually composed of 60~72 amino acids. The amino acids from 1st to 52nd are highly conserved while those after 52nd are highly variable. It has been known that the highly conservation in amino acid sequences of CsrAs/RsmAs are the basis for their similarity in biological functions and regulatory mechanisms. However, the function of the variable region remains unclear. In our previous study, we found that the variable region (from 53rd to 61st amino acids) of Escherichia coli CsrAE. coli has the ability to inhibit the extracellular protease activity of Xanthomonas campestris pathovar campestris (Xcc). In this study, the amino acid residue essential for inhibition of the extracellular protease activity of Xanthomonas campestris pathovar campestris was determined by using alanine substitution analysis. Our results show that K54→A, S60→A and Y61→A substitutions abrogated of the ability of CsrAE. coli inhibiting the extracellular protease activity of Xcc, indicating that K54, S60 and Y61 are essential for CsrE. coli to inhibit the extracellular protease activity of Xcc. Our study provide useful information for understanding the molecular mechanism of CsrAE. coli inhibiting the extracellular protease activity of Xcc.更多还原