Kedzierska S, Staniszewska M, Wegrzyn A, Taylor A
Department of Biochemistry, University of Gdańsk, Poland.
FEBS Lett. 1999 Mar 12;446(2-3):331-7. doi: 10.1016/s0014-5793(99)00154-4.
The submission of Escherichia coli cells to heat-shock (45 degrees C, 15 min) caused the intracellular aggregation of endogenous proteins. In the wt cells the aggregates (the S fraction) disappeared 10 min after transfer to 37 degrees C. In contrast, the S fraction in the dnaK and dnaJ mutant strains was stable during approximately one generation time (45 min). This demonstrated that neither the renaturation nor the degradation of the denatured proteins was possible in the absence of DnaK and DnaJ. The groEL44 and groES619 mutations stabilised the aggregates to a lesser extent. It was shown by the use of cloned genes, dnaK/dnaJ or groEL/groES, producing the corresponding proteins in about 4-fold excess, that the appearance of the S fraction in the wt strain resulted from a transiently insufficient supply of the heat-shock proteins. Overproduction of the GroEL/GroES proteins in dnaK756 or dnaJ259 background prevented the aggregation, however, overproduction of the DnaK/DnaJ proteins did not prevent the aggregation in the groEL44 or groES619 mutant cells although it accelerated the disappearance of the aggregates. The properties of the aggregated proteins are discussed from the point of view of their competence to renaturation/degradation by the heat-shock system.
将大肠杆菌细胞进行热休克处理（45摄氏度，15分钟）会导致内源性蛋白质在细胞内聚集。在野生型细胞中，这些聚集体（S组分）在转移至37摄氏度后10分钟消失。相比之下，dnaK和dnaJ突变株中的S组分在大约一代时间（45分钟）内保持稳定。这表明在缺乏DnaK和DnaJ的情况下，变性蛋白质既无法复性也无法降解。groEL44和groES619突变使聚集体的稳定性略有降低。通过使用克隆基因dnaK/dnaJ或groEL/groES过量表达约4倍相应蛋白质的实验表明，野生型菌株中S组分的出现是由于热休克蛋白的短暂供应不足所致。在dnaK756或dnaJ259背景下过量表达GroEL/GroES蛋白可防止聚集，然而，在groEL44或groES619突变细胞中过量表达DnaK/DnaJ蛋白虽加速了聚集体的消失，但并不能防止聚集。从热休克系统对聚集蛋白质进行复性/降解的能力角度讨论了聚集蛋白质的特性。
