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：1990
卷号：87
期号：4
页码：1511-1515
DOI：10.1073/pnas.87.4.1511
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We have continuously monitored Trp-tRNA(Trp) concentrations in vivo and, in the same cultures, measured rates of protein synthesis in isogenic stringent and relaxed strains. We have also manipulated cellular charged and uncharged [tRNA(Trp)] by two means: (i) the strain used contains a Trp-tRNA synthetase mutation that increases the Km for Trp; thus, varying exogenous Trp varies cellular Trp-tRNA(Trp); and (ii) we have introduced into the mutant strain a plasmid containing the tRNA(Trp) gene behind an inducible promoter; thus, total [tRNA(Trp)] also can be varied depending on length of induction. The use of these conditions, combined with a previously characterized assay system, has allowed us to demonstrate that (i) the rate of incorporation of Trp into protein is proportional to the fraction of tRNA(Trp) that is charged; for any given total [tRNA(Trp)], this rate is also proportional to the [Trp-tRNA(Trp)]; (ii) uncharged tRNA(Trp) inhibits incorporation of Trp into protein; and (iii) rates of incorporation into protein of at least two other amino acids, Lys and Cys, are also sensitive to [Trp-tRNA(Trp)] and are inhibited by uncharged tRNA(Trp). Our results are consistent with models of translational control that postulate modulating polypeptide chain elongation efficiency by varying concentrations of specific tRNAs.
