HEAT-SHOCK REGULATORY GENE HTPR INFLUENCES RATES OF PROTEIN-DEGRADATION AND EXPRESSION OF THE ION GENE IN ESCHERICHIA-COLI
HEAT-SHOCK REGULATORY GENE HTPR INFLUENCES RATES OF PROTEIN-DEGRADATION AND EXPRESSION OF THE ION GENE IN ESCHERICHIA-COLI
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DOI：
10.1073/pnas.81.21.6647
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发表时间：
1984-01-01
期刊：
影响因子：
--
通讯作者：
GOLDBERG, AL
中科院分区：
文献类型：
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作者：
GOFF, SA;CASSON, LP;GOLDBERG, AL
当温度升高时，E.大肠杆菌中的蛋白质降解速率增加，同时也增加了一组热激基因的表达。被温度敏感性抑制子抑制的htpR无义突变体（也称为hin）在30 ℃下显示较低的热休克基因表达。C和未能作出反应的转变，以42.degree。C.发现这些突变体比野生型细胞具有更低的降解异常或不完整蛋白质的能力。这种蛋白水解的减少等于或超过lon突变体中的蛋白水解的减少，lon突变体编码有缺陷的ATP依赖性蛋白酶，蛋白酶La，并且在htpR lon双突变体中特别大。蛋白酶La的活性在野生型细胞中比在30 ℃下生长的htpR突变体中高。C，并在移位至42 °时增加。C仅在野生型中。为了确定htpR是否影响lon基因的转录，利用lon-lacZ操纵子融合。引入htpR突变使lon启动子的转录降低30 ° C。C和37度。C.该缺陷通过携带野生型htpR等位基因的质粒（pFN 97）校正。用乙醇诱导热休克反应对htpR突变体几乎没有影响，但在野生型细胞和携带pFN 97的htpR细胞中刺激lon转录2- 3倍。因此，lon似乎是一个热休克基因，在应激条件下蛋白酶La的合成增加可能有助于防止受损细胞蛋白质的积累。
Upon a shift to high temperature, E. coli increase their rate of protein degradation and also the expression of a set of heat shock genes. Nonsense mutants of htpR (also called hin), suppressed by a temperature-sensitive suppressor, show lower expression of heat shock genes at 30.degree. C and fail to respond to a shift to 42.degree. C. These mutants were found to have a lower capacity to degrade abnormal or incomplete proteins than that of wild-type cells. This reduction in proteolysis equals or exceeds that in lon mutants, which encode a defective ATP-dependent protease, protease La, and is particularly large in htpR lon double mutants. The activity of protease La was higher in wild-type cells than in htpR mutants grown at 30.degree. C and increased upon shift to 42.degree. C only in the wild type. To determine whether htpR influences transcription of the lon gene, a lon-lacZ operon fusion was utilized. Introduction of the htpR mutation reduced transcription from the lon promoter at 30.degree. C and 37.degree. C. This defect was corrected by a plasmid (pFN97) carrying the wild-type htpR allele. Induction of the heat shock response with ethanol had little or no effect in htpR mutants but stimulated lon transcription 2- to 3-fold in wild-type cells and htpR cells carrying pFN97. Thus, lon appears to be a heat shock gene, and increased synthesis of protease La under stressful conditions may help to prevent the accumulation of damaged cellular protein.