Listeria monocytogenes aguA1, but Not aguA2, Encodes a Functional Agmatine Deiminase BIOCHEMICAL CHARACTERIZATION OF ITS CATALYTIC PROPERTIES AND ROLES IN ACID TOLERANCE
Listeria monocytogenes aguA1, but Not aguA2, Encodes a Functional Agmatine Deiminase BIOCHEMICAL CHARACTERIZATION OF ITS CATALYTIC PROPERTIES AND ROLES IN ACID TOLERANCE
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DOI：
10.1074/jbc.m113.477380
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发表时间：
2013-09-13
影响因子：
4.8
通讯作者：
Fang, Weihuan
中科院分区：
文献类型：
--
作者：
Cheng, Changyong;Chen, Jianshun;Fang, Weihuan
单核细胞增生李斯特菌适应低pH环境，因此可以穿过肠道屏障建立全身性感染。L.单核细胞增多症aguA 1和aguA 2编码推定的胍丁胺脱亚胺酶（AgDI）AguA 1和AguA 2。aguA 1和aguA 2的转录在pH 5.0下显著诱导。aguA 1的缺失显着损害其在pH 2.5的胃液和小鼠胃中的存活，而aguA 2的缺失并没有表现出显着的缺陷，在胃液中的存活。以胍丁胺为唯一底物，在大肠杆菌中表达的AguA 1在25 ℃和pH 3.5至10.5的宽范围内是最佳的。重组AguA 2没有脱亚胺酶活性。定点突变显示，所有9个AguA 1突变体完全失去酶活性。AguA 2只有在Cys-157突变为甘氨酸时才获得AgDI活性。AguA 1在相同位点G157 C的突变也使该酶失活。因此，我们发现Gly-157是一个新的残基，不同于已知的催化三联体（Cys-His-Glu/Asp）。单核细胞增多症是酶活性的关键。在这两种AgDI中，只有AguA 1在功能上参与了AgDI途径并介导了L.单核细胞增多症
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. Sitedirected 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.