Straus D B, Walter W A, Gross C A
Department of Bacteriology, University of Wisconsin, Madison 53706.
Genes Dev. 1988 Dec;2(12B):1851-8. doi: 10.1101/gad.2.12b.1851.
Heat shock proteins in Escherichia coli are relatively abundant and some are essential for growth, but the function that they provide is unknown. The observation that heat shock proteins are induced by some abnormal, rapidly degraded polypeptides, and that strains with mutations in the rpoH gene, the positive regulator of heat shock gene expression, are defective in proteolysis, has led to the proposal that heat shock proteins are required for normal degradation of polypeptides. We have investigated this hypothesis by examining the degradation of polypeptide fragments generated by puromycin and the degradation of a nonsense fragment of beta-galactosidase. Mutations in the dnaK, dnaJ, grpE, and groEL heat shock genes result in defective proteolysis. Furthermore, overproduction of heat shock proteins results in enhanced rates of puromycyl fragment decay. The proteolysis defect of the heat shock gene mutants primarily affects energy-dependent protein degradation. These results indicate that at least one general function of heat shock proteins is to contribute to the ability of the cell to degrade abnormal polypeptides.
大肠杆菌中的热休克蛋白相对丰富，其中一些对生长至关重要，但其发挥的功能尚不清楚。热休克蛋白可由一些异常的、快速降解的多肽诱导产生，并且热休克基因表达的正调控因子rpoH基因发生突变的菌株在蛋白水解方面存在缺陷，基于这些观察结果，有人提出热休克蛋白是多肽正常降解所必需的。我们通过研究嘌呤霉素产生的多肽片段的降解以及β-半乳糖苷酶无义片段的降解来验证这一假设。dnaK、dnaJ、grpE和groEL热休克基因的突变会导致蛋白水解缺陷。此外，热休克蛋白的过量表达会提高嘌呤霉素片段的降解速率。热休克基因突变体的蛋白水解缺陷主要影响能量依赖的蛋白质降解。这些结果表明，热休克蛋白的至少一个普遍功能是有助于细胞降解异常多肽的能力。
