Substitution of a Highly Conserved Histidine in the Escherichia coli Heat Shock Transcription Factor, σ ³² , Affects Promoter Utilization In Vitro and Leads to Overexpression of the Biofilm-Associated Flu Protein In Vivo

Abstract

The heat shock sigma factor ( 32 in Escherichia coli) directs the bacterial RNA polymerase to promoters of a specific sequence to form a stable complex, competent to initiate transcription of genes whose products mitigate the effects of exposure of the cell to high temperatures. The histidine at position 107 of 32 is at the homologous position of a tryptophan residue at position 433 of the main sigma factor of E. coli, 70 . This tryptophan is essential for the strand separation step leading to the formation of the initiation-competent RNA polymerase-promoter complex. The heat shock sigma factors of all gammaproteobacteria sequenced have a histidine at this position, while in the alpha-and deltaproteobacteria, it is a tryptophan. In vitro the alaninefor-histidine substitution at position 107 (H107A) destabilizes complexes between the GroE promoter and RNA polymerase containing 32 , implying that H107 plays a role in formation or maintenance of the strandseparated complex. In vivo, the H107A substitution in 32 impedes recovery from heat shock (exposure to 42°C), and it also leads to overexpression at lower temperatures (30°C) of the Flu protein, which is associated with biofilm formation.

HSF1-mediated oxidative stress response to menadione in <i>Saccharomyces cerevisiae</i> KNU5377Y3 by using proteomic approach

“…In addition, HSF is essential for extended longevity in Caenorhabditis elegans [21], oogenesis, early larval development, survival of acute stress response in Drosophila melanogaster [22], and extraembryonic development and stress resistance in mice [17,23]. Escherichia coli HSF (sigma32) provides stress tolerance to both high-and low-temperatures [24]. HSF in plants is required for thermotolerance [25] and stress tolerance to high-light stress and heat-shock, and H 2 O 2 [26] in Arabidopsis and soybeans [27].…”

Control of Gene Expression at a Bacterial Leader RNA, the agn43 Gene Encoding Outer Membrane Protein Ag43 of Escherichia coli

“…Furthermore, all agn43 coding sequences of E. coli strains have been found to be preceded by long leader regions (about 222 to 250 nucleotides [nt], depending on the allele [3]), whose predicted secondary structures reveal the presence of stem-loop structures similar to those of rho-independent transcription terminators (15). However, despite the presence of such putative transcription terminators, the Ag43 protein is abundantly expressed in E. coli (16). Here we examine the role of the leader sequence in the regulation of E. coli K-12 agn43 gene (abbreviated agn K12 ) expression and show that this region contributes to the regulation of expression in addition to the control of transcription initiation by phase variation.…”