乳糖操纵子的分解代谢物阻遏。两种酶的单独阻遏。（注：原文中“Separt epression”拼写有误，可能是“Separate repression”）

Catabolite repression of the lac operon. Separt epressionof two enzymes.

作者信息

Yudkin M D

出版信息

Biochem J. 1969 Sep;114(2):313-9. doi: 10.1042/bj1140313.

DOI:10.1042/bj1140313

PMID:4897463

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1184857/

Abstract

Catabolite repression of beta-galactosidase and of thiogalactoside transacetylase was studied in several strains of Escherichia coli K 12, in an attempt to show whether a single site within the structural genes of the lac operon co-ordinately controls translational repression for the two enzymes. In all experiments the rate of synthesis of the enzymes was compared in glycerol-minimal medium and in glucose-minimal medium. 2. In a wild-type strain, glucose repressed the synthesis of the two enzymes equally. 3. The possibility that repression was co-ordinate was investigated by studies of mutant strains that carry deletions in the genes for beta-galactosidase or galactoside permease or both. In all of the strains with deletions, the repression of thiogalactoside transacetylase persisted, and it is concluded that there is no part of the structural gene for beta-galactosidase that is essential for catabolite repression of thiogalactoside transacetylase. 4. Subculture of one strain through several transfers in rich medium greatly increased its susceptibility to catabolite repression by glucose. It is concluded that unknown features of the genotype can markedly affect sensitivity to catabolite repression. 5. These results make it clear that one cannot draw valid conclusions about the effect of known genotypic differences on catabolite repression from a comparison of two separate strains; to study the effect of a particular genetic change in a lac operon it is necessary to construct a partially diploid strain so that catabolite repression suffered by one lac operon can be compared with that suffered by another. 6. Four such partial diploids were constructed. In all of them catabolite repression of beta-galactosidase synthesized by one operon was equal in extent to catabolite repression of thiogalactoside transacetylase synthesized by the other. 7. Taken together, these results suggest that catabolite repression of beta-galactosidase and thiogalactoside transacetylase is separate but equal.

摘要

对几株大肠杆菌K12菌株中的β-半乳糖苷酶和硫代半乳糖苷转乙酰酶的分解代谢物阻遏作用进行了研究，以试图表明乳糖操纵子结构基因内的单个位点是否协调控制这两种酶的翻译阻遏。在所有实验中，均比较了甘油基本培养基和葡萄糖基本培养基中酶的合成速率。2. 在野生型菌株中，葡萄糖对两种酶的合成抑制程度相同。3. 通过对β-半乳糖苷酶基因或半乳糖苷通透酶基因或两者都有缺失的突变菌株进行研究，探讨了阻遏作用是否协调。在所有有缺失的菌株中，硫代半乳糖苷转乙酰酶的阻遏作用仍然存在，由此得出结论，β-半乳糖苷酶结构基因中不存在对硫代半乳糖苷转乙酰酶分解代谢物阻遏至关重要的部分。4. 一株菌在丰富培养基中传代培养数次后，其对葡萄糖分解代谢物阻遏的敏感性大大增加。得出的结论是，基因型的未知特征可显著影响对分解代谢物阻遏的敏感性。5. 这些结果清楚地表明，通过比较两个单独的菌株，无法就已知基因型差异对分解代谢物阻遏的影响得出有效结论；为了研究乳糖操纵子中特定基因变化的影响，有必要构建一个部分二倍体菌株，以便将一个乳糖操纵子所遭受的分解代谢物阻遏与另一个乳糖操纵子所遭受的进行比较。6. 构建了四个这样的部分二倍体。在所有这些部分二倍体中，一个操纵子合成的β-半乳糖苷酶的分解代谢物阻遏程度与另一个操纵子合成的硫代半乳糖苷转乙酰酶的分解代谢物阻遏程度相同。7. 综合这些结果表明，β-半乳糖苷酶和硫代半乳糖苷转乙酰酶的分解代谢物阻遏是分开的但程度相同。