Trigger Factor and DnaK possess overlapping substrate pools and binding specificities
Trigger Factor and DnaK possess overlapping substrate pools and binding specificities
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DOI：
10.1046/j.1365-2958.2003.03370.x
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发表时间：
2003-03-01
影响因子：
3.6
通讯作者：
Bukau, B
中科院分区：
文献类型：
--
作者：
Deuerling, E;Patzelt, H;Bukau, B
核糖体相关触发因子（TF）和DnaK分子伴侣系统有助于大肠杆菌中新合成蛋白质的折叠。在这里，我们表明，DnaK和TF在体内共享一个共同的底物池。在TF缺陷细胞中，DnaK和DnaJ耗尽的Deltatig中，聚集蛋白的量随着温度的升高而增加，在37 ℃下总计为总可溶性蛋白的10%（约340种蛋白质种类）。类似的蛋白质群体聚集在DnaK耗尽的tig（+）细胞中，尽管程度低得多。从DnaK和DnaJ缺失的Deltatig细胞中分离出94种聚集蛋白，通过质谱鉴定，发现其中包括必需的胞浆蛋白。虽然TF和DnaK识别不同的结合基序，但77%的TF结合肽也与DnaK结合。然而，在新生多肽TF和DnaK竞争结合的情况下，TF具有竞争优势。在体内，TF的损失通过诱导热休克反应来补偿，从而提高DnaK的水平。总之，我们的研究结果表明，在蛋白质折叠的两个机制不同的伴侣的合作是基于其重叠的底物特异性。
Ribosome-associated Trigger Factor (TF) and the DnaK chaperone system assist the folding of newly synthesized proteins in Escherichia coli. Here, we show that DnaK and TF share a common substrate pool in vivo. In TF-deficient cells, Deltatig, depleted for DnaK and DnaJ the amount of aggregated proteins increases with increasing temperature, amounting to 10% of total soluble protein (approximately 340 protein species) at 37degreesC. A similar population of proteins aggregated in DnaK depleted tig(+) cells, albeit to a much lower extent. Ninety-four aggregated proteins isolated from DnaK- and DnaJ-depleted Deltatig cells were identified by mass spectrometry and found to include essential cytosolic proteins.Four potential in vivo substrates were screened for chaperone binding sites using peptide libraries. Although TF and DnaK recognize different binding motifs, 77% of TF binding peptides also associated with DnaK. In the case of the nascent polypeptides TF and DnaK competed for binding, however, with competitive advantage for TF. In vivo, the loss of TF is compensated by the induction of the heat shock response and thus enhanced levels of DnaK. In summary, our results demonstrate that the co-operation of the two mechanistically distinct chaperones in protein folding is based on their overlap in substrate specificities.