Growth-phase-dependent induction of 6-phosphogluconate dehydrogenase and glucose 6-phosphate dehydrogenase in the cyanobacterium Synechococcus sp. PCC7942.
Growth-phase-dependent induction of 6-phosphogluconate dehydrogenase and glucose 6-phosphate dehydrogenase in the cyanobacterium Synechococcus sp. PCC7942.
复制标题
蓝藻聚球藻中 6-磷酸葡萄糖酸脱氢酶和葡萄糖 6-磷酸脱氢酶的生长阶段依赖性诱导。
DOI：
10.1016/0378-1119(91)90590-8
复制
发表时间：
1991
期刊：
影响因子：
3.5
通讯作者：
WolfJr,RE
中科院分区：
文献类型：
--
作者：
BroedelJr,SE;WolfJr,RE
在大多数蓝藻中，在黑暗或能量限制条件下氧化储存碳水化合物的唯一已知途径是单磷酸己糖分流。为了确定在这些条件下分流器使用的增加是否源于相应酶活性水平的增加，我们在聚球菌分批培养过程中测量了生长阶段的影响。对菌株PCC7942的6-磷酸葡萄糖酸脱氢酶（6PGD）和葡萄糖6-磷酸脱氢酶的比活性进行了研究。在培养的指数生长阶段，比活性保持不变，但在过渡到固定阶段时，比活性增加了约5倍。为了确定6PGD在生长阶段依赖性调控下的表达水平，我们在编码6PGD的gdng基因和编码β-半乳糖苷酶（βGal）的大肠杆菌lacZgene之间构建了操纵子和基因融合体。制备了将融合物整合到蓝藻染色体上的菌株，并测定了βGal水平的生长期依赖性。在两种融合菌株的培养物中，βGal的比活性在过渡到固定期时均有所增加，表明生长期依赖于gndmrna水平的调控。在基因结构基因上游携带不同数量DNA的菌株中，生长阶段依赖性诱导6PGD的特性导致启动子和基因限制图谱上调控位点的定位，其序列之前已经确定。所制备的操纵子和蛋白融合载体在蓝藻基因表达研究中具有普遍的应用价值。
In most cyanobacteria, the only known pathway for oxidation of stored carbohydrate in the dark or under energy-limiting conditions is the hexose monophosphate shunt. To determine whether the increased use of the shunt under these conditions derives from an increase in the activity level of the respective enzymes, we measured the effect of growth phase during the growth of batch cultures ofSynechococcussp. strain PCC7942 on the specific activity of 6-phosphogluconate dehydrogenase (6PGD) and glucose 6-phosphate dehydrogenase. The specific activities were constant during the exponential growth phase of the culture, but they increased about fivefold during the transition into stationary phase. As an approach to determining the level of expression at which the growth-phase-dependent regulation of 6PGD level is exerted, we constructed operon and gene fusions between thegndgene, which encodes 6PGD, and theEscherichia coli lacZgene, which encodes β-galactosidase (βGal). Strains harboring the fusions integrated into the cyanobacterial chromosome were prepared, and the growth-phase dependence of βGal level was determined. The specific activity of βGal in cultures of both types of fusion strains increased during the transition into stationary phase, indicating that the growth-phase-dependent regulation is on thegndmRNA level. Characterization of the growth-phase-dependent induction of 6PGD in strains carrying differing amounts of DNA upstream from thegndstructural gene led to the localization of the promoter and the regulatory site on the restriction map of the gene, whose sequence has previously been determined. The operon and protein fusion vectors prepared for this work may be of general use in the study of cyanobacterial gene expression.