Nov 5, 1989

Structural features that underlie the use of bacterial Met-tRNAfMet primarily as an elongator in eukaryotic protein synthesis

The Journal of Biological Chemistry
T WagnerP B Sigler


Met-tRNAfMet from Escherichia coli is utilized efficiently as an elongator tRNA during protein synthesis in the rabbit reticulocyte lysate since it rapidly incorporates its methionyl residue into the same tryptic peptides of rabbit globin as the endogenous Met-tRNAmMet. Therefore, it must lack the structural characteristics that prevent the eukaryotic initiator tRNA from entering elongation. In contrast, E. coli Met-tRNAfMet appears to initiate very poorly since, unlike reticulocyte Met-tRNAiMet, it forms no detectable 43 S preinitiation complexes, and only a very small fraction of the methionine it contributes to polyribosomal peptidyl-tRNA is found at the N terminus. The bacterial fMet-tRNAfMet, which cannot elongate, is utilized for polypeptide chain initiation at a much lower level than the formylated Met-tRNAiMet from eukaryotes. The ability of E. coli Met-tRNAfMet to be used as an elongator and fMet-tRNAfMet as an initiator in the reticulocyte lysate may be considerably underestimated because of the rapid enzymatic hydrolysis of these initiator tRNAs in the lysate. The enzyme hydrolyzes fMet-tRNAfMet and Met-tRNAfMet from E. coli in a strictly Mg2+-dependent manner but not the corresponding species from yeast or rabbit re...Continue Reading

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Mentioned in this Paper

Phenylalanine-Specific tRNA
RNA Conformation
TRNA, peptidyl-
Alkalescens-Dispar Group
Complex (molecular entity)
MT-TA gene
Triplet Codon-amino Acid Adaptor Activity
RNA, Fungal
Transcription Initiation
Reticulocyte Count (Procedure)

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