PMID:9878355

Citation	Lonetto, MA, Rhodius, V, Lamberg, K, Kiley, P, Busby, S and Gross, C (1998) Identification of a contact site for different transcription activators in region 4 of the Escherichia coli RNA polymerase sigma70 subunit. J. Mol. Biol. 284:1353-65
Abstract	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.
Links	PubMed Online version:10.1006/jmbi.1998.2268
Keywords	Alanine; Amino Acid Sequence; AraC Transcription Factor; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Binding Sites; Conserved Sequence; Cyclic AMP Receptor Protein/metabolism; DNA-Directed RNA Polymerases/chemistry; DNA-Directed RNA Polymerases/genetics; DNA-Directed RNA Polymerases/metabolism; Escherichia coli/enzymology; Escherichia coli Proteins; Helix-Turn-Helix Motifs; Iron-Sulfur Proteins/metabolism; Molecular Sequence Data; Promoter Regions, Genetic; Regulatory Sequences, Nucleic Acid; Repressor Proteins/metabolism; Sigma Factor/chemistry; Sigma Factor/genetics; Sigma Factor/metabolism; Structure-Activity Relationship; Trans-Activators/metabolism; Transcription Factors/metabolism; Transcriptional Activation
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECOLI:CRL		GO:0016987: sigma factor activity	ECO:0000314:		F		As figure 2 shows, a series of plasmids were constructed each encoding a different alanine substitution. The complementation by sigma factor 70 C-terminal alanine substitution mutants was similar to the wild-type construct, indicating that the side-chains of most residues in C terminal region are not required for the general functions of sigma factor.	complete CACAO 11650

References

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