Biran D, Brot N, Weissbach H, Ron E Z
Department of Molecular Microbiology and Biotechnology, Tel-Aviv University, Israel.
J Bacteriol. 1995 Mar;177(5):1374-9. doi: 10.1128/jb.177.5.1374-1379.1995.
In Escherichia coli, the growth rate at elevated temperatures is controlled by the availability of endogenous methionine, which is limited because of the temperature sensitivity of the metA gene product, homoserine transsuccinylase (HTS). In order to determine the relationship between this control mechanism and the heat shock response, we estimated the cellular levels of HTS during heat shock by Western (immunoblot) analysis and found an increase following induction by temperature shift and by addition of ethanol or cadmium ions. The elevated level of HTS was a result of transcriptional activation of the metA gene. This activation was heat shock dependent, as it did not take place in rpoH mutants, and probably specific to the metA gene, as another gene of the methionine regulon (metE) was not activated. These results suggest a metabolic link between the two systems that control the response of E. coli to elevated temperatures: the metA gene, which codes for the enzyme responsible for regulating cell growth as a function of temperature elevation (HTS), is transcriptionally activated by the heat shock response.
在大肠杆菌中，高温下的生长速率受内源性甲硫氨酸可用性的控制，由于metA基因产物高丝氨酸转琥珀酰酶（HTS）对温度敏感，内源性甲硫氨酸的量有限。为了确定这种控制机制与热休克反应之间的关系，我们通过蛋白质免疫印迹分析估计了热休克期间HTS的细胞水平，发现温度变化、添加乙醇或镉离子诱导后其水平升高。HTS水平的升高是metA基因转录激活的结果。这种激活依赖于热休克，因为它在rpoH突变体中不发生，并且可能是metA基因特有的，因为甲硫氨酸调节子的另一个基因（metE）未被激活。这些结果表明，控制大肠杆菌对高温反应的两个系统之间存在代谢联系：编码负责根据温度升高调节细胞生长的酶（HTS）的metA基因，被热休克反应转录激活。
