Regnström K, Sauge-Merle S, Chen K, Burgess B K
Department of Molecular Biology, University of California, Irvine, CA 92697-3900, USA.
Proc Natl Acad Sci U S A. 1999 Oct 26;96(22):12389-93. doi: 10.1073/pnas.96.22.12389.
In Azotobacter vinelandii, deletion of the fdxA gene that encodes a well characterized seven-iron ferredoxin (FdI) is known to lead to overexpression of the FdI redox partner, NADPH:ferredoxin reductase (FPR). Previous studies have established that this is an oxidative stress response in which the fpr gene is transcriptionally activated to the same extent in response to either addition of the superoxide propagator paraquat to the cells or to fdxA deletion. In both cases, the activation occurs through a specific DNA sequence located upstream of the fpr gene. Here, we report the identification of the A. vinelandii protein that binds specifically to the paraquat activatable fpr promoter region as the E1 subunit of the pyruvate dehydrogenase complex (PDHE1), a central enzyme in aerobic respiration. Sequence analysis shows that PDHE1, which was not previously suspected to be a DNA-binding protein, has a helix-turn-helix motif. The data presented here further show that FdI binds specifically to the DNA-bound PDHE1.
在棕色固氮菌中，已知编码特征明确的七铁铁氧还蛋白（FdI）的fdxA基因缺失会导致FdI氧化还原伴侣NADPH：铁氧还蛋白还原酶（FPR）的过表达。先前的研究表明，这是一种氧化应激反应，其中fpr基因在细胞中添加超氧化物引发剂百草枯或fdxA缺失时会被转录激活到相同程度。在这两种情况下，激活都是通过位于fpr基因上游的特定DNA序列发生的。在这里，我们报告鉴定出与百草枯可激活的fpr启动子区域特异性结合的棕色固氮菌蛋白为丙酮酸脱氢酶复合体（PDHE1）的E1亚基，这是有氧呼吸中的一种关键酶。序列分析表明，之前未被怀疑为DNA结合蛋白的PDHE1具有螺旋-转角-螺旋基序。这里提供的数据进一步表明FdI与结合在DNA上的PDHE1特异性结合。
