A cycle of binding and release of the DnaK, DnaJ and GrpE chaperones regulates activity of the Escherichia coli heat shock transcription factor sigma(32)
A cycle of binding and release of the DnaK, DnaJ and GrpE chaperones regulates activity of the Escherichia coli heat shock transcription factor sigma(32)
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DOI：
10.1002/j.1460-2075.1996.tb00393.x
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发表时间：
1996-02-01
期刊：
影响因子：
11.4
通讯作者：
Bukau, B
中科院分区：
文献类型：
--
作者：
Gamer, J;Multhaup, G;Bukau, B
由DnaK、DnaJ和GrpE形成的分子伴侣系统介导了大肠杆菌热休克反应的应激依赖性负调节，这可能是通过与RNA聚合酶的热休克启动子特异性σ（32）亚基相关联。分析了DnaK系统与sigma（32）的相互作用。DnaJ和DnaK结合游离σ（32），但不结合RNA聚合酶，解离常数分别为20 nM和5 μ M。DnaJ-sigma（32）复合物的结合和解离速率分别比不存在ATP时的DnaK-sigma（32）复合物高5900倍和20倍。ATP使DnaK-sigma（32）相互作用不稳定。DnaJ通过与σ（32）的快速结合和刺激DnaK结合的ATP的水解，介导DnaK在ATP存在下与σ（32）的有效结合，产生含有ADP的DnaK-DnaJ-σ（32）复合物。GrpE与这些复合物的结合刺激核苷酸释放和随后的ATP复合物解离。我们建议，这个周期的原则也在DnaK系统的其他伴侣活动中发挥作用。DnaK和DnaJ协同抑制热休克基因转录中的sigma（32）活性，GrpE部分逆转这种抑制。这些数据表明，通过DnaK和DnaJ的瞬时缔合可逆抑制σ（32）活性是热休克反应的中心调节元件。
The chaperone system formed by DnaK, DnaJ and GrpE mediates stress-dependent negative modulation of the Escherichia coli heat shock response, probably through association with the heat shock promoter-specific sigma(32) subunit of RNA polymerase. Interactions of the DnaK system with sigma(32) were analysed. DnaJ and DnaK bind free, but not RNA polymerase-bound, sigma(32) with dissociation constants of 20 nM and 5 mu M respectively. Association and dissociation rates of DnaJ-sigma(32) complexes are 5900- and 20-fold higher respectively than those of DnaK-sigma(32) complexes in the absence of ATP. ATP destabilizes DnaK-sigma(32) interactions. DnaJ, through rapid association with sigma(32) and stimulation of hydrolysis of DnaK-bound ATP, mediates efficient binding of DnaK to sigma(32) in the presence of ATP, resulting in DnaK-DnaJ-sigma(32) complexes containing ADP. GrpE binding to these complexes stimulates nucleotide release and subsequent complex dissociation by ATP. We propose that the principles of this cycle also operate in other chaperone activities of the DnaK system. DnaK and DnaJ cooperatively inhibit sigma(32) activity in heat shock gene transcription and GrpE partially reverses this inhibition. These data indicate that reversible inhibition of sigma(32) activity through transient association of DnaK and DnaJ is a central regulatory element of the heat shock response.