Jämsä E, Vakula N, Arffman A, Kilpeläinen I, Makarow M
Institute of Biotechnology, University of Helsinki, Finland.
EMBO J. 1995 Dec 1;14(23):6028-33. doi: 10.1002/j.1460-2075.1995.tb00291.x.
Saccharomyces cerevisiae cells grown at 24 degrees C acquire thermotolerance and survive exposure to 50 degrees C, but only if they are first incubated at 30 degrees C, the temperature where heat shock genes are activated. We show here that the enzymatic activity of a secretory beta-lactamase fusion protein, pre-accumulated at 37 degrees C in the endoplasmic reticulum, was abolished by exposure of the cells to 50 degrees C. When the cells were returned to 24 degrees C, beta-lactamase activity was resumed. Reactivation occurred in the endoplasmic reticulum, but not in the Golgi apparatus. It was dependent on metabolic energy, but did not require de novo protein synthesis. According to co-immunoprecipitation experiments, immuno-globulin-binding protein (BiP/Kar2p) was associated with the fusion protein. We suggest that recovery from thermal insult involves, in addition to cytoplasmic and nuclear events, refolding of heat-damaged proteins in the endoplasmic reticulum by a heat-resistant machinery, which forms part of a fundamental survival mechanism.
在24摄氏度下生长的酿酒酵母细胞获得耐热性并能在暴露于50摄氏度的环境中存活，但前提是它们首先在30摄氏度下培养，即热休克基因被激活的温度。我们在此表明，在内质网中于37摄氏度预先积累的分泌型β-内酰胺酶融合蛋白的酶活性，在细胞暴露于50摄氏度时被消除。当细胞回到24摄氏度时，β-内酰胺酶活性恢复。再激活发生在内质网中，而不是在高尔基体中。它依赖于代谢能量，但不需要从头合成蛋白质。根据共免疫沉淀实验，免疫球蛋白结合蛋白（BiP/Kar2p）与融合蛋白相关。我们认为，除了细胞质和细胞核事件外，热损伤后的恢复还涉及通过一种耐热机制在内质网中对热损伤蛋白质进行重折叠，这是基本生存机制的一部分。
