Chemistry & Biology
Volume 15, Issue 10, 20 October 2008, Pages 1091-1103
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Article
A Full-Length Group 1 Bacterial Sigma Factor Adopts a Compact Structure Incompatible with DNA Binding

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Summary

The σ factors are the key regulators of bacterial transcription initiation. Through direct read-out of promoter DNA sequence, they recruit the core RNA polymerase to sites of initiation, thereby dictating the RNA polymerase promoter-specificity. The group 1 σ factors, which direct the vast majority of transcription initiation during log phase growth and are essential for viability, are autoregulated by an N-terminal sequence known as σ1.1. We report the solution structure of Thermotoga maritima σA σ1.1. We additionally demonstrate by using chemical crosslinking strategies that σ1.1 is in close proximity to the promoter recognition domains of σA. We therefore propose that σ1.1 autoinhibits promoter DNA binding of free σA by stabilizing a compact organization of the σ factor domains that is unable to bind DNA.

CHEMBIO
DNA

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Present address: Department of Chemistry, State University of New York at Albany, 1400 Washington Avenue, Rm LSB1148, Albanym NY 12222, USA