Publication Abstract from PubMed
The "sigma" subunit of prokaryotic RNA polymerase allows gene-specific transcription initiation. Two sigma families have been identified, sigma70 and sigma54, which use distinct mechanisms to initiate transcription and share no detectable sequence homology. Although the sigma70-type factors have been well characterized structurally by x-ray crystallography, no high resolution structural information is available for the sigma54-type factors. Here we present the NMR-derived structure of the C-terminal domain of sigma54 from Aquifex aeolicus. This domain (Thr-323 to Gly-389), which contains the highly conserved RpoN box sequence, consists of a poorly structured N-terminal tail followed by a three-helix bundle, which is surprisingly similar to domains of the sigma70-type proteins. Residues of the RpoN box, which have previously been shown to be critical for DNA binding, form the second helix of an unpredicted helix-turn-helix motif. The homology of this structure with other DNA-binding proteins, combined with previous biochemical data, suggests how the C-terminal domain of sigma54 binds to DNA.
The C-terminal RpoN domain of sigma54 forms an unpredicted helix-turn-helix motif similar to domains of sigma70.,Doucleff M, Malak LT, Pelton JG, Wemmer DE J Biol Chem. 2005 Dec 16;280(50):41530-6. Epub 2005 Oct 6. PMID:16210314[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
