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首页> 美国卫生研究院文献>The Journal of Biological Chemistry >Listeria monocytogenes aguA1 but Not aguA2 Encodes a Functional Agmatine Deiminase
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Listeria monocytogenes aguA1 but Not aguA2 Encodes a Functional Agmatine Deiminase

机译：单核细胞增生李斯特菌aguA1而非aguA2编码功能性胍丁胺脱氨酶

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Listeria monocytogenes is adaptable to low pH environments and therefore crosses the intestinal barrier to establish systemic infections. L. monocytogenes aguA1 and aguA2 encode putative agmatine deiminases (AgDIs) AguA1 and AguA2. Transcription of aguA1 and aguA2 was significantly induced at pH 5.0. Deletion of aguA1 significantly impaired its survival both in gastric fluid at pH 2.5 and in mouse stomach, whereas aguA2 deletion did not show significant defect of survival in gastric fluid. With agmatine as the sole substrate, AguA1 expressed in Escherichia coli was optimal at 25 °C and over a wide range of pH from 3.5 to 10.5. Recombinant AguA2 showed no deiminase activity. Site-directed mutagenesis revealed that all nine AguA1 mutants completely lost enzymatic activity. AguA2 acquired AgDI activity only when Cys-157 was mutated to glycine. AguA1 mutation at the same site, G157C, also inactivated the enzyme. Thus, we have discovered Gly-157 as a novel residue other than the known catalytic triad (Cys-His-Glu/Asp) in L. monocytogenes that is critical for enzyme activity. Of the two putative AgDIs, we conclude that only AguA1 functionally participates in the AgDI pathway and mediates acid tolerance in L. monocytogenes.
机译：单核细胞增生李斯特菌可适应低pH环境，因此可穿过肠道屏障建立全身性感染。单核细胞增生李斯特菌aguA1和aguA2编码假定的胍丁胺脱亚氨酶（AgDI）AguA1和AguA2。在pH 5.0时，明显诱导了aguA1和aguA2的转录。缺失aguA1在pH 2.5的胃液和小鼠胃中均会显着损害其存活，而aguA2缺失并未显示在胃液中存在明显的存活缺陷。以胍丁胺为唯一底物，在大肠杆菌中表达的AguA1在25°C和3.5至10.5的宽pH范围内是最佳的。重组AguA2没有显示脱亚氨酶活性。定点诱变显示所有9个AguA1突变体完全丧失了酶活性。仅当Cys-157突变为甘氨酸时，AguA2才获得AgDI活性。在同一位点G157C处的AguA1突变也使该酶失活。因此，我们在单核细胞增生李斯特氏菌中发现了Gly-157，它是一种新的残基，而不是已知的催化三联体（Cys-His-Glu / Asp），这对酶的活性至关重要。在两个推定的AgDI中，我们得出结论，只有AguA1在功能上参与AgDI途径并介导单​​核细胞增生李斯特菌的耐酸性。

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