Resnekov O, Melin L, Carlsson P, Mannerlöv M, von Gabain A, Hederstedt L
Department of Bacteriology, Karolinska Institute, Stockholm, Sweden.
Mol Gen Genet. 1992 Aug;234(2):285-96. doi: 10.1007/BF00283849.
The primary structure of Bacillus subtilis 105 kDa 2-oxoglutarate dehydrogenase (E10) was deduced from the nucleotide sequence of the odhA gene and confirmed by N-terminal sequence analysis. The protein is highly homologous to E1o of Azotobacter vinelandii and Escherichia coli and of bakers' yeast cells. The 5' end of the odhAB mRNA was determined and the promoter region for the odhAB operon was localized to a 375 bp DNA fragment. The cellular concentration of the 4.5 kb odhAB transcript was found to be growth stage dependent; its concentration during growth in nutrient sporulation medium decreased abruptly at the end of the exponential growth phase and it was not detectable in early stationary phase. This decrease in the cellular concentration of the transcript is not the result of an increased rate of decay of the full-length odhAB mRNA, suggesting that transcription is down-regulated at the end of the exponential growth phase. The cellular concentration of the odhA and odhB gene products, E1o and dihydrolipoamide transsuccinylase (E2o), remains essentially constant throughout the growth curve in nutrient sporulation medium, indicating that both are rather stable proteins. In exponentially growing cells, glucose in nutrient sporulation medium repressed the cellular concentration of the odhAB mRNA, as well as that of E1o and E2o, about four-fold. This effect is most likely the result of a decreased rate of transcription from the odhAB promoter, since neither the stability nor the 5'-end of the transcript were affected by glucose in the medium. It is concluded that the cellular concentration of the 2-oxoglutarate dehydrogenase multienzyme complex (E1o and E2o) is regulated mainly at the transcriptional level.
从odhA基因的核苷酸序列推导了枯草芽孢杆菌105 kDa 2-氧代戊二酸脱氢酶（E10）的一级结构，并通过N端序列分析进行了确认。该蛋白与维涅兰德固氮菌、大肠杆菌和面包酵母细胞的E1o高度同源。确定了odhAB mRNA的5'端，并将odhAB操纵子的启动子区域定位到一个375 bp的DNA片段。发现4.5 kb odhAB转录本的细胞浓度依赖于生长阶段；其在营养芽孢形成培养基中生长期间的浓度在指数生长期结束时突然下降，在早期稳定期无法检测到。转录本细胞浓度的这种下降不是全长odhAB mRNA降解速率增加的结果，这表明转录在指数生长期结束时被下调。在营养芽孢形成培养基中，odhA和odhB基因产物E1o和二氢硫辛酰胺转琥珀酰酶（E2o）的细胞浓度在整个生长曲线中基本保持恒定，表明两者都是相当稳定的蛋白质。在指数生长的细胞中，营养芽孢形成培养基中的葡萄糖使odhAB mRNA以及E1o和E2o的细胞浓度降低了约四倍。这种效应很可能是odhAB启动子转录速率降低的结果，因为培养基中的葡萄糖既不影响转录本的稳定性也不影响其5'端。得出的结论是，2-氧代戊二酸脱氢酶多酶复合物（E1o和E2o）的细胞浓度主要在转录水平受到调节。
