Calvo J M, Matthews R G
Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853.
Microbiol Rev. 1994 Sep;58(3):466-90. doi: 10.1128/mr.58.3.466-490.1994.
The leucine-responsive regulatory protein (Lrp) regulates the expression of more than 40 genes and proteins in Escherichia coli. Among the operons that are positively regulated by Lrp are operons involved in amino acid biosynthesis (ilvIH, serA)), in the biosynthesis of pili (pap, fan, fim), and in the assimilation of ammonia (glnA, gltBD). Negatively regulated operons include operons involved in amino acid catabolism (sdaA, tdh) and peptide transport (opp) and the operon coding for Lrp itself (lrp). Detailed studies of a few members of the regulon have shown that Lrp can act directly to activate or repress transcription of target operons. A substantial fraction of operons regulated by Lrp are also regulated by leucine, and the effect of leucine on expression of these operons requires a functional Lrp protein. The patterns of regulation are surprising and interesting: in some cases activation or repression mediated by Lrp is antagonized by leucine, in other cases Lrp-mediated activation or repression is potentiated by leucine, and in still other cases leucine has no effect on Lrp-mediated regulation. Current research is just beginning to elucidate the detailed mechanisms by which Lrp can mediate such a broad spectrum of regulatory effects. Our view of the role of Lrp in metabolism may change as more members of the regulon are identified and their regulation characterized, but at this point Lrp seems to be important in regulating nitrogen metabolism and one-carbon metabolism, permitting adaptations to feast and to famine.
亮氨酸应答调节蛋白（Lrp）可调控大肠杆菌中40多个基因和蛋白质的表达。受Lrp正向调控的操纵子包括参与氨基酸生物合成的操纵子（ilvIH、serA）、菌毛生物合成的操纵子（pap、fan、fim）以及氨同化的操纵子（glnA、gltBD）。负向调控的操纵子包括参与氨基酸分解代谢的操纵子（sdaA、tdh）和肽转运的操纵子（opp）以及编码Lrp自身的操纵子（lrp）。对该调控子中一些成员的详细研究表明，Lrp可直接作用于激活或抑制靶操纵子的转录。受Lrp调控的操纵子中有很大一部分也受亮氨酸调控，亮氨酸对这些操纵子表达的影响需要功能性的Lrp蛋白。调控模式令人惊讶且有趣：在某些情况下，Lrp介导的激活或抑制会被亮氨酸拮抗，在其他情况下，Lrp介导的激活或抑制会被亮氨酸增强，还有一些情况下亮氨酸对Lrp介导的调控没有影响。目前的研究才刚刚开始阐明Lrp能够介导如此广泛调控效应的详细机制。随着更多调控子成员被鉴定及其调控特性被表征，我们对Lrp在代谢中作用的看法可能会改变，但目前Lrp似乎在调节氮代谢和一碳代谢方面很重要，能使细胞适应富足和饥饿状态。
