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The Escherichia coli threonyl‐tRNA synthetase gene contains a split ribosomal binding site interrupted by a hairpin structure that is essential for autoregulation
Author(s) -
Sacerdot Christine,
Caillet Joel,
Graffe Monique,
Eyermann Flore,
Ehresmann Bernard,
Ehresmann Chantal,
Springer Mathias,
Romby Pascale
Publication year - 1998
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1998.00995.x
Subject(s) - ribosomal binding site , biology , start codon , ribosome , shine dalgarno sequence , eukaryotic translation , transfer rna , translation (biology) , genetics , ribosomal protein , binding site , a site , messenger rna , gene , microbiology and biotechnology , rna
The expression of the gene encoding Escherichia coli threonyl‐tRNA synthetase (ThrRS) is negatively autoregulated at the translational level. ThrRS binds to its own mRNA leader, which consists of four structural and functional domains: the Shine–Dalgarno (SD) sequence and the initiation codon region (domain 1); two upstream hairpins (domains 2 and 4) connected by a single‐stranded region (domain 3). Using a combination of in vivo and in vitro approaches, we show here that the ribosome binds to thrS mRNA at two non‐contiguous sites: region −12 to +16 comprising the SD sequence and the AUG codon and, unexpectedly, an upstream single‐stranded sequence in domain 3. These two regions are brought into close proximity by a 38‐nucleotide‐long hairpin structure (domain 2). This domain, although adjacent to the 5′ edge of the SD sequence, does not inhibit ribosome binding as long as the single‐stranded region of domain 3 is present. A stretch of unpaired nucleotides in domain 3, but not a specific sequence, is required for efficient translation. As the repressor and the ribosome bind to interspersed domains, the competition between ThrRS and ribosome for thrS mRNA binding can be explained by steric hindrance.