RAMAKRISHNAN T, ADELBERG E A
J Bacteriol. 1965 Mar;89(3):654-60. doi: 10.1128/jb.89.3.654-660.1965.
Ramakrishnan, T. (Yale University, New Haven, Conn.), and Edward A. Adelberg. Regulatory mechanisms in the biosynthesis of isoleucine and valine. II. Identification of two operator genes. J. Bacteriol. 89:654-660. 1965.-A tightly clustered set of five structural genes governs the synthesis of the five enzymes of isoleucine and valine biosynthesis in Escherichia coli. Three of the genes governing transaminase B, dehydrase, and threonine deaminase, are controlled by a single operator locus, designated oprA. The structural gene governing the condensing enzyme is controlled by a second operator locus, designated oprB. Both oprA and oprB have been shown to regulate structural genes which are cis, but not trans, to their own operator. No mutations have yet been found which affect the level of reductoisomerase, but the existence of a third operator controlling the synthesis of this enzyme can be inferred. Enzyme derepression resulting from mutations in oprA confers resistance to high levels of valine. Derepression of the condensing enzyme resulting from mutations in oprB confers resistance to low levels of valine, and to alpha-aminobutyric acid. The significance of these findings with respect to the valine sensitivity of E. coli strain K-12 is discussed.
拉马克里什南，T.（耶鲁大学，康涅狄格州纽黑文），以及爱德华·A.阿德尔伯格。异亮氨酸和缬氨酸生物合成中的调控机制。II. 两个操纵基因的鉴定。《细菌学杂志》89:654 - 660。1965年。——一组紧密聚集的五个结构基因控制着大肠杆菌中异亮氨酸和缬氨酸生物合成的五种酶的合成。控制转氨酶B、脱水酶和苏氨酸脱氨酶的三个基因由一个单一的操纵位点控制，命名为oprA。控制缩合酶的结构基因由第二个操纵位点控制，命名为oprB。已表明oprA和oprB都调控与其自身操纵子顺式而非反式的结构基因。尚未发现影响还原异构酶水平的突变，但可以推断存在控制该酶合成的第三个操纵子。oprA突变导致的酶去阻遏赋予对高水平缬氨酸的抗性。oprB突变导致的缩合酶去阻遏赋予对低水平缬氨酸和α - 氨基丁酸的抗性。讨论了这些发现对于大肠杆菌K - 12菌株缬氨酸敏感性的意义。
