Sauter M, Sawers R G
Lehrstuhl für Mikrobiologie der Universität München, FRG.
Mol Microbiol. 1990 Mar;4(3):355-63. doi: 10.1111/j.1365-2958.1990.tb00603.x.
The act gene of Escherichia coli encodes the pyruvate formate-lyase-activating enzyme which is necessary for the post-translational modification of pyruvate formate-lyase. The gene is located 191 bp downstream from the pfl structural gene. Northern blot analysis revealed that the act transcript is monocistronic and that transcription is independent of pfl gene expression. Through mapping of the 5' and 3' ends of the act transcript, sequences could be identified showing similarity to both an Escherichia coli sigma 70 promoter and to a rho-independent transcription terminator. Expression of the act gene was analysed with the aid of chromosomally integrated transcriptional and translational lacZ fusions. The results verified that the act gene is transcribed from its own promoter and that expression of the gene is essentially constitutive. Anaerobiosis led only to a two-fold increase in expression over that observed in aerobically grown cells and this elevated expression was independent of the transcriptional regulator, Fnr. Moreover, effectors such as pyruvate and nitrate, which substantially influence anaerobic transcription of the pfl gene, did not affect act gene expression.
大肠杆菌的act基因编码丙酮酸甲酸裂解酶激活酶，该酶是丙酮酸甲酸裂解酶翻译后修饰所必需的。该基因位于pfl结构基因下游191 bp处。Northern印迹分析表明，act转录本是单顺反子的，且转录独立于pfl基因表达。通过对act转录本5′和3′末端的定位，可以鉴定出与大肠杆菌σ70启动子和ρ非依赖性转录终止子均相似的序列。借助染色体整合的转录和翻译lacZ融合体分析了act基因的表达。结果证实，act基因从其自身启动子转录，且该基因的表达基本上是组成型的。厌氧条件下，其表达量仅比需氧生长细胞中的表达量增加两倍，且这种表达升高与转录调节因子Fnr无关。此外，丙酮酸和硝酸盐等效应物虽然对pfl基因的厌氧转录有显著影响，但并不影响act基因的表达。
