Liberek K, Wall D, Georgopoulos C
Department of Molecular Biology, University of Gdansk, Poland.
Proc Natl Acad Sci U S A. 1995 Jul 3;92(14):6224-8. doi: 10.1073/pnas.92.14.6224.
In Escherichia coli the heat shock response is under the positive control of the sigma 32 transcription factor. Three of the heat shock proteins, DnaK, DnaI, and GrpE, play a central role in the negative autoregulation of this response at the transcriptional level. Recently, we have shown that the DnaK and DnaJ proteins can compete with RNA polymerase for binding to the sigma 32 transcription factor in the presence of ATP, by forming a stable DnaJ-sigma 32-DnaK protein complex. Here, we report that DnaJ protein can catalytically activate DnaK's ATPase activity. In addition, DnaJ can activate DnaK to bind to sigma 32 in an ATP-dependent reaction, forming a stable sigma 32-DnaK complex. Results obtained with two DnaJ mutants, a missense and a truncated version, suggest that the N-terminal portion of DnaJ, which is conserved in all family members, is essential for this activation reaction. The activated form of DnaK binds preferentially to sigma 32 versus the bacteriophage lambda P protein substrate.
在大肠杆菌中，热休克反应受σ32转录因子的正调控。三种热休克蛋白，即DnaK、DnaI和GrpE，在转录水平上对该反应的负向自我调节中起核心作用。最近，我们发现，在ATP存在的情况下，DnaK和DnaJ蛋白可以通过形成稳定的DnaJ-σ32-DnaK蛋白复合物，与RNA聚合酶竞争结合σ32转录因子。在此，我们报告DnaJ蛋白可以催化激活DnaK的ATP酶活性。此外，DnaJ可以在ATP依赖性反应中激活DnaK与σ32结合，形成稳定的σ32-DnaK复合物。用两个DnaJ突变体（一个错义突变体和一个截短体）获得的结果表明，DnaJ的N端部分在所有家族成员中保守，对这种激活反应至关重要。与噬菌体λP蛋白底物相比，激活形式的DnaK优先结合σ32。
