Regulation of the tryptophan operon by readthrough of UGA termination codons |
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Authors: | H. Engelberg-Kulka L. Dekel M. Israeli-Reches |
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Affiliation: | Department of Molecular Biology, Institute of Microbiology, Hebrew University-Hadassah Medical School, Jerusalem, Israel. |
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Abstract: | The regulation of the synthesis of operon enzymes was studied in streptomycin-resistant mutants temperature-sensitive for UGA suppression by normal tRNATrp. Our mutants carry a allele that when transferred to a different genetic background causes repression of trp operon enzyme synthesis at both low (35°C) and high (42°C) temperatures; however, in our mutants with an excess of tryptophan and at increased temperatures enzyme synthesis is derepressed. Based on our results and the sequence data of the R gene [Singleton et al. (1980) Nucleic Acids Res., 8, 1551–1560], we offer a model for the involvement of the limited misreading of UGA codons by normal charged tRNATrp in the autogenous regulation of the R gene expression. The UGA readthrough process may be a regulatory amplifier of the effect of tryptophan starvation. |
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Keywords: | 5-MT 5-methyltryptophan ASase anthranilate synthetase TSase tryptophan synthetase |
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