Simon M, Apirion D
Genetics. 1972 May;71(1):1-18. doi: 10.1093/genetics/71.1.1.
In a temperature-sensitive mutant of Escherichia coli, beta-galactosidase cannot be induced at the nonpermissive temperature (43 degrees C) without the addition of exogenous 3', 5'-cyclic AMP (cAMP), although the intracellular concentration of this nucleotide is normal. This specific effect of cAMP is probably general in this strain for those operons which are controlled by the cAMP receptor protein and cAMP, but not for other parts of the chromosome. The lac mRNA produced at 43 degrees C in absence of cAMP is transcribed from the correct DNA strand and it directs the synthesis of enzymatically inactive material cross-reacting with beta-galactosidase. Experiments separating transcription from translation by using rifampicin, suggest that cAMP exerts its effect during initiation of transcription or translation of lac mRNA, but does not affect the propagation of either the messenger or of the beta-galactosidase polypeptide chain.
在大肠杆菌的一个温度敏感突变体中,若不添加外源3',5'-环磷酸腺苷(cAMP),β-半乳糖苷酶在非允许温度(43℃)下就无法被诱导,尽管该核苷酸的细胞内浓度是正常的。cAMP的这种特定作用在该菌株中对于那些由cAMP受体蛋白和cAMP控制的操纵子可能是普遍存在的,但对染色体的其他部分则不然。在43℃且无cAMP的情况下产生的lac mRNA是从正确的DNA链转录而来的,并且它指导合成与β-半乳糖苷酶发生交叉反应的无酶活性物质。使用利福平将转录与翻译分开进行的实验表明,cAMP在lac mRNA转录或翻译起始过程中发挥作用,但不影响信使或β-半乳糖苷酶多肽链的延伸。