IDENTIFICATION OF THE LEXA GENE-PRODUCT OF ESCHERICHIA-COLI-K-12
IDENTIFICATION OF THE LEXA GENE-PRODUCT OF ESCHERICHIA-COLI-K-12
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DOI：
10.1073/pnas.76.12.6147
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发表时间：
1979-01-01
影响因子：
11.1
通讯作者：
HARPER, JE
中科院分区：
文献类型：
--
作者：
LITTLE, JW;HARPER, JE
大肠杆菌 lexA 基因编码的产物对于 recA 基因的诱导和各种细胞功能的表达（包括诱变和原噬菌体诱导）很重要。作为 lexA 函数生化分析的起点，.lambda 家族。分离并表征了携带 lexA 基因的 lexA+、lexA3、lexA3 spr-54 和 lexA3 spr-55 等位基因的转导噬菌体。检查了这些噬菌体合成的多肽。 .lambda.lexA+ 产生了一种大小为 24 千道尔顿 (kd) 的独特蛋白质。 .lambda.lexA3编码对野生型功能占主导地位的蛋白质的活性突变形式，产生了尺寸稍大的25kd蛋白质。后一种蛋白质是突变的lexA3基因产物，因为在lexA3中携带琥珀突变的.lambda.lexA3 spr-55在具有琥珀抑制子的宿主中产生25-kd蛋白质，但在无抑制子的宿主中则不产生25-kd蛋白质。在携带多拷贝 lexA3 质粒的宿主中，既没有产生 25-kd 也没有产生 24-kd 蛋白质。该结果表明lexA是自动调节的并且由.lambda.lexA+产生的24-kd蛋白质的表达受到相同的控制。该证据和其他证据表明 24-kd 蛋白质是野生型 lexA+ 基因的产物。
The E. coli lexA gene encodes a product important in induction of the recA gene and the expression of various cellular functions, including mutagenesis and prophage induction. As a start in a biochemical analysis of the lexA function, a family of .lambda. transducing phages carrying lexA+, lexA3, lexA3 spr-54 and lexA3 spr-55 alleles of the lexA gene was isolated and characterized. Polypeptides synthesized by these phages were examined. .lambda.lexA+ made a distinctive protein 24 kilodaltons (kd) in size. .lambda.lexA3, which encodes an active mutant form of the protein dominant to wild-type function, made a slightly larger protein 25 kd in size. The latter protein was the mutant lexA3 gene product by the fact that .lambda.lexA3 spr-55, which carries an amber mutation in lexA3, made the 25-kd protein in hosts with an amber suppressor but not in a suppressor-free host. In hosts carrying a multicopy lexA3 plasmid, neither the 25-kd nor the 24-kd protein was made. This result suggests that lexA is autoregulated and that expression of the 24-kd protein made by .lambda.lexA+ is subject to the same controls. This and other evidence argues that the 24-kd protein is the product of the wild-type lexA+ gene.