Rodriguez Fernanda, Arsène-Ploetze Florence, Rist Wolfgang, Rüdiger Stefan, Schneider-Mergener Jens, Mayer Matthias P, Bukau Bernd
Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
Mol Cell. 2008 Nov 7;32(3):347-58. doi: 10.1016/j.molcel.2008.09.016.
Central to the transcriptional control of the Escherichia coli heat shock regulon is the stress-dependent inhibition of the sigma(32) subunit of RNA polymerase by reversible association with the DnaK chaperone, mediated by the DnaJ cochaperone. Here we identified two distinct sites in sigma(32) as binding sites for DnaK and DnaJ. DnaJ binding destabilizes a distant region of sigma(32) in close spatial vicinity of the DnaK-binding site, and DnaK destabilizes a region in the N-terminal domain, the primary target for the FtsH protease, which degrades sigma(32) in vivo. Our findings suggest a molecular mechanism for the DnaK- and DnaJ-mediated inactivation of sigma(32) as part of the heat shock response. They furthermore demonstrate that DnaK and DnaJ binding can induce conformational changes in a native protein substrate even at distant sites, a feature that we propose to be of general relevance for the action of Hsp70 chaperone systems.
大肠杆菌热休克调节子转录控制的核心是，通过与DnaJ共伴侣介导的DnaK伴侣可逆结合，对RNA聚合酶的σ(32)亚基进行应激依赖性抑制。在此，我们确定了σ(32)中两个不同的位点作为DnaK和DnaJ的结合位点。DnaJ结合使DnaK结合位点附近空间上较远的σ(32)区域不稳定，而DnaK使N端结构域中的一个区域不稳定，该区域是FtsH蛋白酶的主要作用靶点，FtsH蛋白酶在体内降解σ(32)。我们的研究结果提示了一种分子机制，即作为热休克反应的一部分，DnaK和DnaJ介导σ(32)失活。它们还证明，即使在远距离位点，DnaK和DnaJ结合也能诱导天然蛋白质底物的构象变化，我们认为这一特征与Hsp70伴侣系统的作用普遍相关。
