Isomeric aminoacyl tRNAs are both bound by elongation factor Tu

S. M. Hecht, K. Hock Tan, A. C. Chinault, P. Arcari

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Abstract

Recent suggestions that elongation factor Tu (EF Tu) is specific for 2' omicron aminoacyl tRNA, as compared with the 3' isomer, prompted the authors to assay [3H]aminoacyl tRNAs from E. coli terminating in 2' or 3' deoxyadenosine for binding to EF Tu to determine the possible positional specificity of the factor. Binding of modified aminoacyl tRNAs to EF Tu x GTP was measured both as a function of the ability of EF Tu x GTP to diminish the rate of chemical deacylation of [3H]aminoacyl tRNAs and by gel filtration of the individual ternary complexes. Fifteen different tRNA isoacceptors were tested by the deacylation procedure, including 3 (tRNAAsp, tRNACys, and tRNATyr) for which isomeric modified aminoacyl tRNAs were available. All of the modified aminoacyl tRNAs were protected from deacylation, although generally to a lesser extent than the corresponding unmodified species. Six modified tRNA isoacceptors (including tRNATrp and tRNATyr, for which both modified aminoacyl tRNAs were accessible by enzymatic aminoacylation) were used in gel filtration experiments to permit direct measurement of the individual aminoacyl tRNA EF Tu x GTP complexes. These experiments were also done in the presence of equimolar amounts of the corresponding unmodified [14C]aminoacyl tRNAs, and the relative affinities for a limiting amount of EF Tu x GTP were measured. The results were completely consistent with those obtained by the deacylation procedure and indicated that EF Tu can bind to both positional isomers of aminoacyl tRNA with no obvious preference for either.

Original languageEnglish (US)
Pages (from-to)437-441
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume74
Issue number2
DOIs
StatePublished - 1977

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