Institute of Biochemistry and Molecular Biology, School of Life Science, National Yang-Ming University, Taipei, Taiwan, Republic of China.
J Bacteriol. 2012 Sep;194(18):4995-5001. doi: 10.1128/JB.00778-12. Epub 2012 Jul 13.
The Bacillus subtilis ald gene encodes L-alanine dehydrogenase, which catalyzes the NAD(+)-dependent deamination of L-alanine to pyruvate for the generation of energy and is required for normal sporulation. The transcription of ald is induced by alanine, but the mechanism underlying alanine induction remains unknown. Here we report that a gene (formerly yukF and now designated adeR) located upstream of ald is essential for the basal and alanine-inducible expression of ald. The disruption of the adeR gene caused a sporulation defect, whereas the complementation of an adeR mutation with an intact adeR gene restored the sporulation ability. adeR expression was not subject to autoregulation and alanine induction. Deletion and mutation analyses revealed that an inverted repeat, centered at position -74.5 relative to the transcriptional initiation site of ald, was required for ald expression and also likely served as a ρ-independent transcription terminator. Electrophoretic mobility shift assays showed that purified His-tagged AdeR was a specific DNA-binding protein and that this inverted repeat was required for AdeR binding. AdeR shows no significant amino acid sequence similarity to the known transcriptional activators of ald genes from other bacteria. AdeR appears to be a member of the PucR family of transcriptional regulators. Its orthologs of unknown function are present in some other Bacillus species. Collectively, these findings support the notion that AdeR is a transcriptional activator which mediates ald expression in response to alanine availability and is important for normal sporulation in B. subtilis.
枯草芽孢杆菌 ald 基因编码 L-丙氨酸脱氢酶，该酶催化 NAD(+)依赖的 L-丙氨酸脱氨生成丙酮酸，为细胞提供能量，并且对于正常孢子形成是必需的。ald 的转录受丙氨酸诱导，但丙氨酸诱导的机制尚不清楚。在这里，我们报告位于 ald 上游的一个基因（以前称为 yukF，现在命名为 adeR）对于 ald 的基础表达和丙氨酸诱导表达是必需的。adeR 基因的缺失导致孢子形成缺陷，而用完整的 adeR 基因互补 adeR 突变恢复了孢子形成能力。adeR 表达不受自身调控和丙氨酸诱导。缺失和突变分析表明，位于 ald 转录起始位点上游-74.5 位置的反向重复序列对于 ald 表达是必需的，并且可能充当 ρ 独立转录终止子。电泳迁移率变动分析表明，纯化的 His 标记的 AdeR 是一种特异性 DNA 结合蛋白，该反向重复序列是 AdeR 结合所必需的。AdeR 与来自其他细菌的 ald 基因的已知转录激活因子没有显著的氨基酸序列相似性。AdeR 似乎是 PucR 家族转录调节因子的一员。其功能未知的同源物存在于其他一些芽孢杆菌物种中。总之，这些发现支持了这样的观点，即 AdeR 是一种转录激活因子，它介导 ald 表达对丙氨酸可用性的响应，并且对于枯草芽孢杆菌的正常孢子形成是重要的。
