Prüss B M, Wolfe A J
Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois 60153.
Mol Microbiol. 1994 Jun;12(6):973-84. doi: 10.1111/j.1365-2958.1994.tb01085.x.
We investigated the relationship between Escherichia coli flagellar expression and the regulation of acetyl phosphate synthesis and degradation. Using cells either wild type for acetyl phosphate metabolism or defective for phosphotransacetylase or acetate kinase, or both, we measured flagellar expression and the intracellular concentration of acetyl phosphate relative to growth phase and temperature. Under the conditions tested, we found that elevated levels of acetyl phosphate corresponded to inhibition of flagellar synthesis. To extend these observations, we measured the intracellular concentration of acetyl-CoA, the level of expression from the pta and ackA promoters, and the activities of phosphotransacetylase and acetate kinase derived from cell lysates. Relative to increasing culture density, acetyl-CoA levels and expression from both the pta and ackA promoters decreased. Relative to increasing temperature, expression from the ackA promoter decreased and phosphotransacetylase activity increased. In contrast, temperature had little or no effect on either acetate kinase activity or expression from the pta promoter. We propose that cells regulate intracellular acetyl phosphate concentrations relative to growth phase and temperature by modulating the availability of acetyl-CoA, the expression of ackA, and the activity of phosphotransacetylase.
我们研究了大肠杆菌鞭毛表达与乙酰磷酸合成和降解调控之间的关系。我们使用了在乙酰磷酸代谢方面为野生型、磷酸转乙酰酶或乙酸激酶缺陷型或两者均缺陷型的细胞，测量了鞭毛表达以及相对于生长阶段和温度的细胞内乙酰磷酸浓度。在所测试的条件下，我们发现乙酰磷酸水平升高与鞭毛合成受到抑制相对应。为了扩展这些观察结果，我们测量了细胞内乙酰辅酶A的浓度、pta和ackA启动子的表达水平，以及源自细胞裂解物的磷酸转乙酰酶和乙酸激酶的活性。相对于培养密度的增加，乙酰辅酶A水平以及pta和ackA启动子的表达均下降。相对于温度的升高，ackA启动子的表达下降，而磷酸转乙酰酶活性增加。相比之下，温度对乙酸激酶活性或pta启动子的表达几乎没有影响。我们提出，细胞通过调节乙酰辅酶A的可用性、ackA的表达以及磷酸转乙酰酶的活性，来相对于生长阶段和温度调节细胞内乙酰磷酸的浓度。
