Identification of a contact site for different transcription activators in region 4 of the Escherichia coli RNA polymerase sigma70 subunit.
The sigma subunit of RNA polymerase orchestrates basal transcription by first binding to core RNA polymerase and then recognizing promoters. Using a series of 16 alanine-substitution mutations, we show that residues in a narrow region of Escherichia coli sigma70 (590 to 603) are involved in transcription activation by a mutationally altered CRP derivative, FNR and AraC. Homology modeling of region 4 of sigma70 to the closely related NarL or 434 Cro proteins, suggests that the five basic residues implicated in activation are either in the C terminus of a long recognition helix that includes residues recognizing the -35 hexamer region of the promoter, or in the subsequent loop, and are ideally positioned to permit interaction with activators. The only substitution that has a significant effect on activator-independent transcription is at R603, indicating that this residue of sigma70 may play a distinct role in transcription initiation.
Lonetto
M A
MA
Department of Stomatology, University of California at San Francisco, San Francisco, CA, 94143, USA.
Rhodius
V
V
Lamberg
K
K
Kiley
P
P
Busby
S
S
Gross
C
C
D000409:Alanine; D000595:Amino Acid Sequence; D051777:AraC Transcription Factor; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D017124:Conserved Sequence; D002373:Cyclic AMP Receptor Protein / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D019077:Helix-Turn-Helix Motifs; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000378:metabolism; D012808:Sigma Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation
D051777:AraC Transcription Factor; C497371:AraC protein, E coli; D001426:Bacterial Proteins; D002373:Cyclic AMP Receptor Protein; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D007506:Iron-Sulfur Proteins; D012097:Repressor Proteins; D012808:Sigma Factor; D015534:Trans-Activators; D014157:Transcription Factors; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases; D000409:Alanine