atxA controls Bacillus anthracis capsule synthesis via acpA and a newly discovered regulator, acpB
atxA controls Bacillus anthracis capsule synthesis via acpA and a newly discovered regulator, acpB
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DOI：
10.1128/jb.186.2.307-315.2004
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发表时间：
2004-01-01
影响因子：
3.2
通讯作者：
Koehler, TM
中科院分区：
文献类型：
--
作者：
Drysdale, M;Bourgogne, A;Koehler, TM
已经报道了两种调控基因acpA和atxA控制炭疽芽孢杆菌荚膜生物合成操纵子capBCAD的表达。atxA基因位于毒力质粒pXO 1上，而pXO 2携带acpA和cap基因。acpA被认为是cap操纵子的主要调节因子，因为它是pXO 1（-）pXO 2（+）菌株中荚膜基因表达所必需的。atxA对于毒素基因转录至关重要，但也与cap基因的控制有关。调节蛋白的分子功能是未知的。我们在一个基因完整的pXO 1（+）pXO 2（+）菌株中检测了cap基因的表达。我们的结果表明，另一个pXO 2基因acpB（以前称为pXO 2 -53;登录号NC002146.1：49418-50866）在cap表达中起作用。预测的AcpB的氨基酸序列与AcpA的相似性为62%，与AtxA的相似性为50%。对cap基因转录的评估显示，在pXO 1（+）pXO 2（+）acpB-无效突变体中，cap表达不受影响，而在同基因aepA突变体中，cap表达略有降低。然而，帽基因表达废除acpA acpB双突变体。突变体的胶囊合成的显微镜检查证实了这些发现。acpA和acpB的表达是由atxA控制的;在atxA突变体中，acpA和acpB的胶囊合成和转录显著减少。这些数据表明，在一个菌株含有两种毒力质粒，atxA是胶囊合成的主要调节剂和控制capBCAD表达间接，通过积极调节acpA和acpB。
Two regulatory genes, acpA and atxA, have been reported to control expression of the Bacillus anthracis capsule biosynthesis operon capBCAD. The atxA gene is located on the virulence plasmid pXO1, while pXO2 carries acpA and the cap genes. acpA has been viewed as the major regulator of the cap operon because it is essential for capsule gene expression in a pXO1(-) pXO2(+) strain. atxA is essential for toxin gene transcription but has also been implicated in control of the cap genes. The molecular functions of the regulatory proteins are unknown. We examined cap gene expression in a genetically complete pXO1(+) pXO2(+) strain. Our results indicate that another pXO2 gene, acpB (previously called pXO2-53; accession no. NC002146.1:49418-50866), has a role in cap expression. The predicted amino acid sequence of AcpB is 62% similar to that of AcpA and 50% similar to that of AtxA. Assessment of cap gene transcription revealed that cap expression was not affected in a pXO1(+) pXO2(+) acpB-null mutant and was slightly reduced in an isogenic aepA mutant. However, cap gene expression was abolished in an acpA acpB double mutant. Microscopic examination of capsule synthesis by the mutants corroborated these findings. acpA and acpB expression is controlled by atxA; capsule synthesis and transcription of acpA and acpB were markedly reduced in an atxA mutant. The data suggest that, in a strain containing both virulence plasmids, atxA is the major regulator of capsule synthesis and controls capBCAD expression indirectly, via positive regulation of acpA and acpB.