GROWTH-RATE REGULATION OF ESCHERICHIA-COLI ACETYL COENZYME-A CARBOXYLASE, WHICH CATALYZES THE 1ST COMMITTED STEP OF LIPID BIOSYNTHESIS
GROWTH-RATE REGULATION OF ESCHERICHIA-COLI ACETYL COENZYME-A CARBOXYLASE, WHICH CATALYZES THE 1ST COMMITTED STEP OF LIPID BIOSYNTHESIS
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DOI：
10.1128/jb.175.2.332-340.1993
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发表时间：
1993-01-01
影响因子：
3.2
通讯作者：
CRONAN, JE
中科院分区：
文献类型：
--
作者：
LI, SJ;CRONAN, JE
乙酰辅酶A （CoA）羧化酶催化丙二酰辅酶A的合成，丙二酰辅酶A是脂肪酸合成的第一中间体。大肠杆菌酶由位于大肠杆菌染色体上三个不同位置的四个亚基编码。accBC基因位于最小72位的小操纵子中，而accA和accD分别位于最小4.3位和最小50位。我们通过定量Northern （RNA）印迹分析检测了编码大肠杆菌乙酰辅酶a羧化酶亚基（accA， accBC和accD）的基因在各种生长条件下的表达。我们发现acc基因的转录水平与细胞生长速度之间存在直接关联。在营养上升和下降实验以及将固定相培养物稀释到新鲜培养基中也获得了一致的结果。我们还通过引物延伸确定了accA和accD mrna的5'端，并对先前报道的accBC启动子进行了转录融合分析。在这些基因的启动子区域发现了几个有趣的特征，包括弯曲的DNA序列和accBC操纵子异常长的先导mRNA中的开放阅读框，accA和accD mRNA先导区域中潜在的茎环结构，以及所有三个启动子共有的富含gc的序列，然后是富含at的序列。此外，accA和accD都位于复杂的基因簇中。例如，accA启动子位于上游的polC基因（编码DNA聚合酶III催化亚基）中，这表明存在其他调控机制。
Acetyl coenzyme A (CoA) carboxylase catalyzes the synthesis of malonyl-CoA, the first intermediate of fatty acid synthesis. The Escherichia coli enzyme is encoded by four subunits located at three different positions on the E. coli chromosome. The accBC genes lie in a small operon at min 72, whereas accA and accD are located at min 4.3 and 50, respectively. We examined the expression of the genes that encode the E. coli acetyl-CoA carboxylase subunits (accA, accBC, and accD) under a variety of growth conditions by quantitative Northern (RNA) blot analysis. We found a direct correlation between the levels of transcription of the acc genes and the rate of cellular growth. Consistent results were also obtained upon nutritional upshift and downshift experiments and upon dilution of stationary-phase cultures into fresh media. We also determined the 5' end of the accA and accD mRNAs by primer extension and did transcriptional fusion analysis of the previously reported accBC promoter. Several interesting features were found in the promoter regions of these genes, including a bent DNA sequence and an open reading frame within the unusually long leader mRNA of the accBC operon, potential stem-loop structures in the accA and accD mRNA leader regions, and a stretch of GC-rich sequences followed by AT-rich sequences common to all three promoters. In addition, both accA and accD are located in complex gene clusters. For example, the accA promoter was localized within the upstream polC gene (which encodes the DNA polymerase III catalytic subunit), suggesting that additional regulatory mechanisms exist.