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Updated: Aug 10, 2026

Isolation of Translating Ribosomes Containing Peptidyl-tRNAs for Functional and Structural Analyses
Published on: February 25, 2011
Requirement for an upstream element for optimal transcription of a bacterial tRNA gene
Abstract:
Bacterial promoters are the sites at the 5' end of each gene that bind RNA polymerase and direct the initiation of transcription. The functional elements of Escherichia coli promoters are two highly conserved sequences, each about six nucleotides long, usually centred at sites -10 and -35, +1 being the initiating nucleotide. We have been interested in the structure of promoters of genes that are subject to stringent control, that is whose expression is reduced in conditions of amino acid shortage, such as rRNA and tRNA genes. We have therefore mapped the sequences involved in promoting in vivo transcription of a bacterial tRNATyr (tyrT) gene by fusing the tyrT promoter region to a galactokinase (galK) gene, and using in vivo expression of galactokinase activity to measure promoter strength. We show here that efficient expression from the tyrT promoter requires specific sequences upstream of the canonical promoter elements, and we suggest that these sequences constitute an extended promoter structure.
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