Escherichia coli rpoS gene has an internal secondary translation initiation region

Pochi Ramalingam Subbarayan, Malancha Sarkar

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Sigma S (σs) encoded by rpoS in Escherichia coli is a stationary phase specific sigma subunit of the RNA polymerase holoenzyme. Widespread among the E. coli K12 strains is an amber mutation that prematurely terminates σs. These rpoSAm mutants would be expected to show no σs activity. However, suppressor free rpoSAm mutants retain an intermediate catalase activity, a sigma S controlled function. By analyzing the sequence of the rpoS gene we hypothesize that a 277 amino acids long Δ1-53σs of about 30kDa can be translated from an internal secondary translation initiation region (STIR, AGGGAGN11GUG) that is located downstream of the amber codon. By cloning this rpoSAm gene, following the expression, function, and N-terminal sequence of this mutant protein, we report the presence of a functional internal STIR in E. coli rpoS, from where a truncated but nevertheless functional form of σs can be synthesized.

Original languageEnglish (US)
Pages (from-to)294-299
Number of pages6
JournalBiochemical and biophysical research communications
Issue number2
StatePublished - Jan 9 2004


  • Δ1-53 σ
  • σ
  • σ
  • Amber mutants
  • GASP mutants
  • Internal translation initiation
  • rpoSAm
  • STIR

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology


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