Unden G, Duchene A
Arch Microbiol. 1987 Mar;147(2):195-200. doi: 10.1007/BF00415284.
The role of adenosine 3',5'-monophosphate (cAMP) and of the Fnr protein, a transcriptional regulator of anaerobic electron transport, in the expression of anaerobic respiration of Escherichia coli was investigated. Under conditions of fermentation or anaerobic respiration intracellular cAMP was formed in concentrations up to 4.6 nmol/g protein. From the enzymes of the anaerobic electron transfer chain from glycerol-3-P to fumarate only the expression of glycerol-3-P dehydrogenase (Freedberg WB, Lin ECC (1973) J Bacteriol 115:816-823), but not that of fumarate reductase required cAMP. Isolated Fnr protein, which has been suggested to be an additional site of action of cAMP under anaerobic conditions did not bind cAMP. It is concluded that cAMP in anaerobic growth like in aerobic growth acts as the effector of CRP and that catabolite repression plays an important regulatory role in anaerobic catabolism. The Fnr protein was present in constant amounts (0.06 mg/g cellular protein) and in constant molar mass (Mr 30,000) in aerobically and in anaerobically grown bacteria. This result excluded regulation of the activity of the Fnr protein by a change of concentration or by processing of the protein.
研究了3',5'-环磷酸腺苷（cAMP）和Fnr蛋白（一种厌氧电子传递的转录调节因子）在大肠杆菌厌氧呼吸表达中的作用。在发酵或厌氧呼吸条件下，细胞内形成的cAMP浓度高达4.6 nmol/g蛋白质。在从甘油-3-磷酸到延胡索酸的厌氧电子传递链的酶中，只有甘油-3-磷酸脱氢酶的表达（Freedberg WB，Lin ECC（1973）J Bacteriol 115:816 - 823）需要cAMP，而延胡索酸还原酶的表达则不需要。有人提出在厌氧条件下Fnr蛋白是cAMP的另一个作用位点，但分离出的Fnr蛋白并不结合cAMP。得出的结论是，厌氧生长中的cAMP与好氧生长中一样，作为CRP的效应物，并且分解代谢物阻遏在厌氧分解代谢中起重要的调节作用。在好氧和厌氧生长的细菌中，Fnr蛋白的含量恒定（0.06 mg/g细胞蛋白），摩尔质量也恒定（Mr 30,000）。这一结果排除了通过浓度变化或蛋白质加工来调节Fnr蛋白活性的可能性。
