A cluster of constitutive mutations affecting the C-terminus of the redox-sensitive SoxR transcriptional activator.
A cluster of constitutive mutations affecting the C-terminus of the redox-sensitive SoxR transcriptional activator.
复制标题
影响氧化还原敏感 SoxR 转录激活因子 C 末端的一组组成型突变。
DOI：
10.1093/nar/22.15.2958
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发表时间：
1994
影响因子：
14.9
通讯作者：
Demple,B
中科院分区：
文献类型：
--
作者：
Nunoshiba,T;Demple,B
大肠杆菌氧化应激调节子基因（sodA、zwf、fumC、nfo等）的激活由两阶段调节系统介导：氧化还原敏感的SoxR蛋白转录激活oxS基因，其产物然后刺激调节子基因的转录。以前的实验表明，soxR基因的有限3′端截短导致了oxRS的组成性表达。来自最初分离的soxf 1 S组成型菌株的oxR基因的DNA序列分析（Greenbergetal.等人（1990）Proc. Acad. Sci. USA 87，6181 - 6185）揭示了三个等位基因编码聚集在SoxR的C末端附近的氨基酸取代或链终止。另外两个单一的氨基酸取代的组成型等位基因映射到螺旋-转角-螺旋基序和一个未知的功能区域的中心的多肽，分别。在编码SoxR FeS中心的半胱氨酸的区域内，在SoxR或SoxS启动子中，或在SoxS结构基因中，未发现组成型突变。由于仅9个SoxR残基（136-144;全长SoxR = 154个残基）的框内缺失产生了强大的组成型等位基因，因此似乎SoxR C-末端的一小段使蛋白质保持在非活性状态。相反，一个完整的C-末端显然是不需要的基因激活SoxR。
Activation of Escherichia coli oxidative stress regulon genes (sodA, zwf, fumC, nfo, etc.) is mediated by a twostage regulatory system: the redox-sensitive SoxR protein transcriptionally activates thesoxSgene, whose product then stimulates transcription of the regulon genes. Previous experiments showed that limited 3′ truncation ofsoxRgene causes constitutivesoxRSexpression. DNA sequence analysis of thesoxRgenes from the soxflS-constitutive strains isolated originally (Greenbergetal. (1990)Proc. Natl. Acad. Sci. USA87, 6181 – 6185) revealed that three alleles encode amino acid substitutions or a chain termination clustered near the C-terminus of SoxR. Two other single-amino-acid substitutions in constitutive alleles mapped to the helix-turn-helix motif and to a region of unknown function in the center of the polypeptide, respectively. No constitutive mutation was found within the region encoding the cysteines of the SoxR FeS center, in the soxR or soxS promoters, or in the soxS structural gene. Since an in-frame deletion of just nine SoxR residues (136–144; full-length SoxR = 154 residues) gave rise to a powerful constitutive allele, it appears that a small segment of the SoxR C-terminus maintains the protein in the inactive state. Conversely, an intact C-terminus is evidently not required for gene activation by SoxR.