期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1975
卷号：72
期号：9
页码：3453-3457
DOI：10.1073/pnas.72.9.3453
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：An activator-attenuator model of positive control, a s opposed to the classic repressor-operator model of negative control, is proposed for the major operon-specific mechanism governing expression of the histidine gene cluster of Salmonella typhimurium. Evidence for this mechanism is derived from experiments performed with a coupled in vitro transcription-translation system, as well as with a minimal in vitro transcription system [Kasai, T. (1974) Nature 249, 523--527]. The product (G enzyme, or N-1-[5'-phosphoribosyl]adenosine triphosphate:pyrophosphate phosphoribosyltransferase; EC 2.4.2.17 ) of the first structural gene (hisG) of the histidine operon is not involved in the positive control mechanism. However, a possible role for G enzyme as an accessory negative control element interacting at the attenuator can be accommodated in our model. The operon-specific mechanism works in conjunction with an independent mechanism involving guanosine 5'-diphosphate 3'-diphosphate (ppGpp) which appears to be a positive effector involved in regulating amino-acid-producing systems, in general [Stephens, J.C., Artz, S.W. & Ames, B.N. (1975) Proc. Nat. Acad. Sci. USA, in press].
