文章基本信息

标题：Effects of Guanosine Tetraphosphate, Guanosine Pentaphosphate, and β-γ Methylenyl-Guanosine Pentaphosphate on Gene Expression of Escherichia coli In Vitro
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作者：Huey-Lang Yang ; Geoffrey Zubay ; Elo Urm 等
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：1974
卷号：71
期号：1
页码：63-67
DOI：10.1073/pnas.71.1.63
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The effects of guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp), both produced by E. coli, were measured on the activities of several genes in a cell-free system. Gene activity is measured as gene-directed synthesis of biochemically competent protein or transfer RNA. Both ppGpp and pppGpp stimulated the activities of the ara, lac, and trp operons and inhibited the arg operon. Production of transfer-RNATyr was unaffected by moderate levels of either ppGpp or pppGpp and only slightly inhibited at higher levels of ppGpp. Since the cell-free reaction mixtures hydrolyze pppGpp to ppGpp, we performed similar studies with a hydrolysis-resistant analog of pppGpp, the {beta}-{gamma} methylenyl derivative (pcppGpp). In general, pcppGpp shows the same inhibitory potency as pppGpp for the arg operon, but lacks the stimulatory effects on the ara, lac, and trp operons. This result suggests that the stimulation of these gene activities is specific for ppGpp. Under similar conditions, pppGpp and ppGpp show a slight inhibitory effect on the messenger-directed synthesis of {beta}-galactosidase and no effect on the messenger-directed synthesis of MS2 viral-coat protein. These observations, together with the fact that in the same system these nucleotides affect coupled transcription and translation, lead us to surmise that the activities of pppGpp and ppGpp are exerted at the level of RNA polymerase activity.
关键词：pppGpp ; ppGpp ; cell-free protein synthesis