Levels of DnaK and DnaJ provide tight control of heat shock gene expression and protein repair in Escherichia coli
Levels of DnaK and DnaJ provide tight control of heat shock gene expression and protein repair in Escherichia coli
复制标题
DnaK 和 DnaJ 水平可严格控制大肠杆菌中的热休克基因表达和蛋白质修复
作者：
T. Tomoyasu;T. Ogura;T. Tatsuta;B. Bukau
热休克基因在大肠杆菌中的表达受转录激活因子、RNA聚合酶的σ32亚基和负调制剂的拮抗作用调控。调节剂是DnaK伴侣系统，它使σ32失活和不稳定，FtsH蛋白酶，它主要负责σ32的降解。一个尚未证实的假设是，通过与错误折叠的蛋白质结合，调节因子的隔离程度决定了热休克基因转录的水平。通过改变IPTG和阿拉伯糖控制启动子中表达dnaK、dnaJ和ftsH的细胞中的调节剂浓度，验证了这一假设。DnaK和DnaJ co - chaperone水平的小幅升高（<野生型的1.5倍）导致中温σ32水平和活性下降，热休克反应关闭速度加快。它们水平的小幅度下降会产生相反的效应，而且会降低热变性蛋白的再折叠效率和在热冲击温度下的生长。少于1500分子的DnaK系统底物，结构不稳定的萤火虫荧光素酶，导致热休克蛋白水平升高，延长热休克反应的关闭阶段。相比之下，FtsH水平的降低增加了σ32水平，但累积的σ32水平不活跃，表明单独封存FtsH不能有效地诱导热休克反应。因此，DnaK和DnaJ构成了大肠杆菌热休克反应的主要应激感应和转导系统，能够以高灵敏度检测蛋白质错误折叠。
The expression of heat shock genes in Escherichia coli is regulated by the antagonistic action of the transcriptional activator, the σ32 subunit of RNA polymerase, and negative modulators. Modulators are the DnaK chaperone system, which inactivates and destabilizes σ32, and the FtsH protease, which is largely responsible for σ32 degradation. A yet unproven hypothesis is that the degree of sequestration of the modulators through binding to misfolded proteins determines the level of heat shock gene transcription. This hypothesis was tested by altering the modulator concentration in cells expressing dnaK, dnaJ and ftsH from IPTG and arabinose‐controlled promoters. Small increases in levels of DnaK and the DnaJ co‐chaperone (< 1.5‐fold of wild type) resulted in decreased level and activity of σ32 at intermediate temperature and faster shut‐off of the heat shock response. Small decreases in their levels caused inverse effects and, furthermore, reduced the refolding efficiency of heat‐denatured protein and growth at heat shock temperatures. Fewer than 1500 molecules of a substrate of the DnaK system, structurally unstable firefly luciferase, resulted in elevated levels of heat shock proteins and a prolonged shut‐off phase of the heat shock response. In contrast, a decrease in FtsH levels increased the σ32 levels, but the accumulated σ32 was inactive, indicating that sequestration of FtsH alone cannot induce the heat shock response efficiently. DnaK and DnaJ thus constitute the primary stress‐sensing and transducing system of the E. coli heat shock response, which detects protein misfolding with high sensitivity.
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非洲爪蟾卵母细胞热休克（应激）反应的变性蛋白诱导剂的表征。
DOI：
--
发表时间：
1994
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Mifflin,LC;Cohen,RE
通讯作者：
Cohen,RE
影响因子：
10.5
作者：
David B. Straus;William Walter;C A Gross
通讯作者：
David B. Straus;William Walter;C A Gross
DOI：
10.1073/pnas.92.6.2126
发表时间：
1995-03-14
影响因子：
11.1
作者：
KIM, DH;OUYANG, H;LI, GC
通讯作者：
LI, GC
影响因子：
10.5
作者：
STRAUS, D;WALTER, W;GROSS, CA
通讯作者：
GROSS, CA