Lim C J, Hwang W, Park E H, Fuchs J A
Department of Biochemistry, Kangwon National University, South Korea.
Biochim Biophys Acta. 1994 Jun 21;1218(2):250-3. doi: 10.1016/0167-4781(94)90024-8.
The Escherichia coli serC-aroA operon encodes biosynthetic enzymes for unrelated amino acid biosynthetic pathways leading to the synthesis of serine and the aromatic amino acids. A serC-aroA-lac translational fusion was constructed in the vector pMC1403. Synthesis of beta-galactosidase from the serC-aroA-lac fusion was found to be enhanced in the presence of lactose as the sole carbon source. This enhancement was not observed in strains containing a cya or crp mutant. However, the exogenous addition of cAMP greatly increased the beta-galactosidase synthesis in the cya mutant strain. The serC-aroA mRNA content, analyzed by a dot blot assay, also appeared to increase in the serC+ aroA+ cells after the exogenous addition of cAMP. These findings unambiguously indicate that the expression of the serC-aroA operon is positively controlled by cAMP.
大肠杆菌serC - aroA操纵子编码参与不相关氨基酸生物合成途径的生物合成酶，这些途径分别导致丝氨酸和芳香族氨基酸的合成。在载体pMC1403中构建了serC - aroA - lac翻译融合体。发现在以乳糖作为唯一碳源的情况下，serC - aroA - lac融合体中β - 半乳糖苷酶的合成增强。在含有cya或crp突变体的菌株中未观察到这种增强现象。然而，外源添加cAMP可极大地增加cya突变体菌株中β - 半乳糖苷酶的合成。通过斑点印迹分析，serC + aroA +细胞中外源添加cAMP后，serC - aroA mRNA含量似乎也有所增加。这些发现明确表明serC - aroA操纵子的表达受到cAMP的正调控。
