Substitution of a highly conserved histidine in the Escherichia coli heat shock transcription factor, sigma32, affects promoter utilization in vitro and leads to overexpression of the biofilm-associated flu protein in vivo.

Abstract

The heat shock sigma factor (sigma(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 sigma(32) is at the homologous position of a tryptophan residue at position 433 of the main sigma factor of E. coli, sigma(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 alanine-for-histidine substitution at position 107 (H107A) destabilizes complexes between the GroE promoter and RNA polymerase containing sigma(32), implying that H107 plays a role in formation or maintenance of the strand-separated complex. In vivo, the H107A substitution in sigma(32) impedes recovery from heat shock (exposure to 42 degrees C), and it also leads to overexpression at lower temperatures (30 degrees C) of the Flu protein, which is associated with biofilm formation.

• Authors: Olga V Kourennaia, Pieter L Dehaseth
• Journal: Journal of bacteriology (J Bacteriol) Vol. 189 Issue 23 Pg. 8430-6 (Dec 2007) ISSN: 1098-5530 [Electronic] United States
• PMID: 17921304 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• DNA-Binding Proteins
• Escherichia coli Proteins
• Flu protein, E coli
• Heat Shock Transcription Factors
• Heat-Shock Proteins
• Sigma Factor
• Transcription Factors
• heat-shock sigma factor 32
• Histidine

Topics

• Amino Acid Sequence
• Amino Acid Substitution (genetics)
• Biofilms
• Conserved Sequence (genetics)
• DNA-Binding Proteins (chemistry, genetics, metabolism)
• Escherichia coli (genetics, metabolism)
• Escherichia coli Proteins (genetics, metabolism)
• Gene Expression Regulation, Bacterial
• Heat Shock Transcription Factors
• Heat-Shock Proteins
• Histidine (genetics)
• Promoter Regions, Genetic (genetics)
• Sigma Factor (genetics, metabolism)
• Transcription Factors (chemistry, genetics, metabolism)