Quay S C, Oxender D L
J Bacteriol. 1976 Sep;127(3):1225-38. doi: 10.1128/jb.127.3.1225-1238.1976.
The repression and derepression of leucine, isoleucine, and valine transport in Escherichia coli K-12 was examined by using strains auxotrophic for leucine, isoleucine, valine, and methionine. In experiments designed to limit each of these amino acids separately, we demonstrate that leucine limitation alone derepressed the leucine-binding protein, the high-affinity branched-chain amino acid transport system (LIV-I), and the membrane-bound, low-affinity system (LIV-II). This regulation did not seem to involve inactivation of transport components, but represented an increase in the differential rate of synthesis of transport components relative to total cellular proteins. The apparent regulation of transport by isoleucine, valine, and methionine reported elsewhere was shown to require an intact leucine, biosynthetic operon and to result from changes in the level of leucine biosynthetic enzymes. A functional leucyl-transfer ribonucleic acid synthetase was also required for repression of transport. Transport regulation was shown to be essentially independent of ilvA or its gene product, threonine deaminase. The central role of leucine or its derivatives in cellular metabolism in general is discussed.
通过使用对亮氨酸、异亮氨酸、缬氨酸和蛋氨酸营养缺陷的菌株，研究了大肠杆菌K-12中亮氨酸、异亮氨酸和缬氨酸转运的阻遏和去阻遏情况。在旨在分别限制这些氨基酸中的每一种的实验中，我们证明仅亮氨酸限制就会使亮氨酸结合蛋白、高亲和力支链氨基酸转运系统（LIV-I）和膜结合的低亲和力系统（LIV-II）去阻遏。这种调节似乎不涉及转运成分的失活，而是代表转运成分相对于总细胞蛋白的合成差异率增加。其他地方报道的异亮氨酸、缬氨酸和蛋氨酸对转运的明显调节被证明需要完整的亮氨酸生物合成操纵子，并且是由亮氨酸生物合成酶水平的变化引起的。转运的阻遏还需要有功能的亮氨酰转移核糖核酸合成酶。已表明转运调节基本上不依赖于ilvA或其基因产物苏氨酸脱氨酶。本文还讨论了亮氨酸或其衍生物在一般细胞代谢中的核心作用。
