Identification of the Amidotransferase AsnB1 as Being Responsible for meso-Diaminopimelic Acid Amidation in Lactobacillus plantarum Peptidoglycan
Identification of the Amidotransferase AsnB1 as Being Responsible for meso-Diaminopimelic Acid Amidation in Lactobacillus plantarum Peptidoglycan
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DOI：
10.1128/jb.05060-11
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发表时间：
2011-11-01
影响因子：
3.2
通讯作者：
Chapot-Chartier, Marie-Pierre
中科院分区：
文献类型：
--
作者：
Bernard, Elvis;Rolain, Thomas;Chapot-Chartier, Marie-Pierre
植物乳杆菌（Lactobacillus plantarum）的肽聚糖（PG）含有修饰的中二氨基亚苯甲酸（meso-diaminopimelic acid, mDAP）。这种PG修饰的功能作用从未在任何细菌物种中被描述过，除了它对先天免疫系统受体对PG识别的影响。对植物l.s plantarum基因组中携带PG生物合成基因的基因座进行的硅分析显示，murE基因编码催化mDAP向udp - n - muramyl - d -谷氨酸PG前体添加的连接酶，而asnB1基因编码一种假定的具有n端氨基转移酶结构域的天冬酰胺合成酶，两者共定位。通过基因破坏和互补实验，我们发现asnB1是参与mDAP酰胺化的氨基转移酶。PG结构分析表明，mDAP酰胺化在L， d -羧肽酶DacB活性的控制中起关键作用。此外，mDAP酰胺化缺陷的突变株在生长和细胞形态上受到强烈影响，出现丝化和细胞链化，而dacb阴性菌株的表型与野生型菌株非常相似。这些结果表明，mDAP酰胺化可能在分离过程的控制中起关键作用。
The peptidoglycan (PG) of Lactobacillus plantarum contains amidated meso-diaminopimelic acid (mDAP). The functional role of this PG modification has never been characterized in any bacterial species, except for its impact on PG recognition by receptors of the innate immune system. In silico analysis of loci carrying PG biosynthesis genes in the L. plantarum genome revealed the colocalization of the murE gene, which encodes the ligase catalyzing the addition of mDAP to UDP-N-muramoyl-D-glutamate PG precursors, with asnB1, which encodes a putative asparagine synthase with an N-terminal amidotransferase domain. By gene disruption and complementation experiments, we showed that asnB1 is the amidotransferase involved in mDAP amidation. PG structural analysis revealed that mDAP amidation plays a key role in the control of the L,D-carboxypeptidase DacB activity. In addition, a mutant strain with a defect in mDAP amidation is strongly affected in growth and cell morphology, with filamentation and cell chaining, while a DacB-negative strain displays a phenotype very similar to that of a wild-type strain. These results suggest that mDAP amidation may play a critical role in the control of the septation process.