Open AccessEnhancement of the Synthesis of RpoE and StpA by Polyamines at the Level of Translation in Escherichia coli under Heat Shock Conditions
Author(s) -
Yusuke Terui,
Kyohei Higashi,
Yuzuru Tabei,
Hideyuki Tomitori,
Kaneyoshi Yamamoto,
Akira Ishihama,
Kazuei Igarashi,
Keiko Kashiwagi
Publication year - 2009
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.00387-09
Subject(s) - biology , polyamine , ribosomal binding site , eukaryotic translation , protein biosynthesis , start codon , spermidine , heat shock , biochemistry , escherichia coli , ribosome , translation (biology) , heat shock protein , microbiology and biotechnology , messenger rna , rna , gene , enzyme
Proteins whose synthesis is enhanced by polyamines at the level of translation were identified with a polyamine-requiring mutant cultured in the presence of 0.1% glucose and 0.02% glutamate at 42°C. Polyamines had a greater effect on cell growth at 42°C than at 37°C. At 42°C, the synthesis of RpoE (σ24 ) and StpA, which are involved in the transcription of a number of heat shock response genes, was stimulated by polyamines at the level of translation. In therpoE andstpA mRNAs, a Shine-Dalgarno (SD) sequence is located at 13 and 12 nucleotides, respectively, upstream of the initiation codon AUG. When the SD sequences were moved to the more common position 7 nucleotides upstream of the initiation codon AUG, the degree of polyamine stimulation was reduced, although the level of RpoE and StpA synthesis was markedly increased. The mechanism underlying polyamine stimulation of RpoE synthesis was then studied. Polyamine stimulation of RpoE synthesis was reduced by changing the bulged-out structure in the initiation site ofrpoE mRNA, although the level of RpoE synthesis increased. A selective structural change of this bulged-out region induced by spermidine at 42°C was observed by circular dichroism. Polyamine stimulation of fMet-tRNA binding to ribosomes at 42°C also disappeared by changing the bulged-out structure in the initiation site ofrpoE mRNA. The results suggest that polyamines enhance the synthesis of RpoE by changing the bulged-out structure in the initiation site ofrpoE mRNA.