Carothers A M, Heincz M C, McFall E
J Bacteriol. 1980 Apr;142(1):185-90. doi: 10.1128/jb.142.1.185-190.1980.
In the D-serine deaminase system of Escherichia coli, which is regulated by positive control, we have fouand a complete lack of trans activation in vivo with multicopy dsd hybrid plasmids. A PLASmid carrying the regulatory gene, dsdC+, did not promote expression of chromosomal dsdCO+A+ loci, nor did a chromosomal dsdC+ gene promote expression of plasmid-borne dsdC delta O+A+ (dsd regulatory gene negative) restriction fragments. However, hybrid plasmids that comprise the entire dsd system (dsdC+O+A+) are highly inducible for the enzyme. These dsd hybrid plasmid deoxyribonucleic acids functioned well as templates in the in vitro coupled transcription-translation system. In vitro-synthesized dsdC+ protein promoted expression of the dsdA+ operation efficiently. Exogenously purified dsdC+ protein also activated expression of several dsdC delta O+A+ plasmid deoxyribonucleic acid templates in vitro. An explanation that reconciles these results with previous dominance studies is presented.
在受正调控的大肠杆菌D-丝氨酸脱氨酶系统中，我们发现多拷贝dsd杂交质粒在体内完全缺乏反式激活作用。携带调控基因dsdC⁺的质粒不会促进染色体dsdC⁰⁺A⁺位点的表达，染色体dsdC⁺基因也不会促进质粒携带的dsdCΔO⁺A⁺（dsd调控基因阴性）限制片段的表达。然而，包含整个dsd系统（dsdC⁺O⁺A⁺）的杂交质粒对该酶具有高度诱导性。这些dsd杂交质粒脱氧核糖核酸在体外偶联转录-翻译系统中作为模板功能良好。体外合成的dsdC⁺蛋白有效地促进了dsdA⁺操纵子的表达。外源纯化的dsdC⁺蛋白在体外也激活了几种dsdCΔO⁺A⁺质粒脱氧核糖核酸模板的表达。本文提出了一个将这些结果与先前显性研究相协调的解释。
