Spx-dependent oxygen sensing mechanism in lactic acid bacteria

在本研究中，我们分析了变形链球菌依赖spx的氧感机制。Spx是一种rna结合蛋白，最初在枯草芽孢杆菌中发现。当变形链球菌的半胱氨酸残基被氧化时，SpxA和SpxB与RNA聚合酶的α亚基结合更强。细胞内Spx降解途径分析表明，SpxB被ClpXP蛋白酶复合物降解，而细胞内SpxA浓度不变，不受ClpXP蛋白酶的影响。SpxB在clpor突变体中的浓度增加不影响抗氧化蛋白的表达谱。这些结果表明，Spx的半胱氨酸残基的氧化，而不是细胞的Spx浓度，可能在变形链球菌的氧感知中起关键作用。

In thepresent study, we analyzed Spx-dependent oxygensensing mechanism of Streptococcus mutans. Spx is a RNA-binding protein originally identified in Bacillus subtilis. Both SpxA and SpxB of S. mutanswere shown to more strongly bind to alpha-subunit of RNA polymerase when cysteineresidues of these proteins were oxidized. Analysis of cellular Spx degradation pathway demonstrated that SpxB was degraded by ClpXP protease complexwhilecellular SpxA concentrations were constant and not affected by ClpXP protease. Increased concentrationsof SpxB in clpPor clpXmutant didn't affect the expression profileof antioxidative proteins. Theseresultsindicated that the oxidation of cysteineresidues of Spx, rather than cellularSpx concentrations, might play a critical role in oxygen sensing of S. mutans.