EmbA is an essential arabinosyltransferase in Mycobacterium tuberculosis
EmbA is an essential arabinosyltransferase in Mycobacterium tuberculosis
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DOI：
10.1099/mic.0.2007/012153-0
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发表时间：
2008-01-01
期刊：
影响因子：
2.8
通讯作者：
Parish, Tanya
中科院分区：
文献类型：
--
作者：
Amin, Anita G.;Goude, Renan;Parish, Tanya
Emb蛋白（EmbA、EmbB、EmbC）是参与分枝杆菌细胞壁的生物发生的分枝杆菌阿拉伯糖基转移酶。预测EmbA和EmbB作为异二聚体一致地起作用。EmbA和EmbB参与细胞壁多糖阿拉伯半乳聚糖中关键末端六阿拉伯糖苷基序[Ara beta（1-> 2）Ara alpha（1-> 5）][Ara beta（1-> 2）Ara alpha（1-> 3）] Ara alpha（1-> 5）Ara alpha 1->（Ara（6））的形成。在耻垢分枝杆菌中进行的研究显示，emBA或embB中具有破坏的突变体是可行的，尽管生长速率受到影响。相比之下，我们在这里证明，emBA是结核分枝杆菌中的一个必需基因，因为染色体基因的缺失只能在整合载体上提供第二个功能性拷贝时才能实现。对M. M. smegalloy。结核杆菌emBA证实它编码功能性阿拉伯糖基转移酶。我们鉴定了M的启动子。结核杆菌embA位于该基因的上游，表明它独立于上游基因embC表达。当在M中测定时，来自P-embA（Mtb）的启动子活性低7倍。与M.结核分枝杆菌，表明后者不是一个很好的宿主进行遗传分析的M。结核emBA表达。P-embA（Mtb）的活性保持恒定的整个生长阶段和应激处理后，虽然它是减少缺氧incluced非复制持久性。乙胺丁醇暴露对P-emBA（Mtb）活性无影响。这些数据表明M.结核分枝杆菌embA编码一种功能性阿拉伯糖基转移酶，该酶在结核分枝杆菌中组成型表达并起关键作用。结核
The Emb proteins (EmbA, EmbB, EmbC) are mycobacterial arabinosyltransferases involved in the biogenesis of the mycobacterial cell wall. EmbA and EmbB are predicted to work in unison as a heterodimer. EmbA and EmbB are involved in the formation of the crucial terminal hexaarabinoside, motif [Ara beta(1 -> 2)Ara alpha(1 -> 5)] [Ara beta(1 -> 2)Ara alpha(1 -> 3)]Ara alpha(1 -> 5)Ara alpha 1 ->(Ara(6)) in the cell wall polysaccharide arabinogalactan. Studies conducted in Mycobacterium smegmatis revealed that mutants with disruptions in embA or embB are viable, although the growth rate was affected. In contrast, we demonstrate here that embA is an essential gene in Mycobacterium tuberculosis, since a deletion of the chromosomal gene could only be achieved when a second functional copy was provided on an integrated vector. Complementation of an embA mutant of M. smegmatis by M. tuberculosis embA confirmed that it encodes a functional arabinosyltransferase. We identified a promoter for M. tuberculosis embA located immediately upstream of the gene, indicating that it is expressed independently from the upstream gene, embC. Promoter activity from P-embA(Mtb) was sevenfold lower when assayed in M. smegmatis compared to M. tuberculosis, indicating that the latter is not a good host for genetic analysis of M. tuberculosis embA expression. P-embA(Mtb) activity remained constant throughout growth phases and after stress treatment, although it was reduced during hypoxia-incluced non-replicating persistence. Ethambutol exposure had no effect on P-embA(Mtb) activity. These data demonstrate that M. tuberculosis embA encodes a functional arabinosyltransferase which is constitutively expressed and plays a critical role in M. tuberculosis.