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In bacteria, the binding of a single protein, the initiation factor sigma, to a multi-subunit RNA polymerase core enzyme results in the formation of a holoenzyme, the active form of RNA polymerase essential for transcription initiation. Here we report the crystal structure of a bacterial RNA polymerase holoenzyme from Thermus thermophilus at 2.6 A resolution. In the structure, two amino-terminal domains of the sigma subunit form a V-shaped structure near the opening of the upstream DNA-binding channel of the active site cleft. The carboxy-terminal domain of sigma is near the outlet of the RNA-exit channel, about 57 A from the N-terminal domains. The extended linker domain forms a hairpin protruding into the active site cleft, then stretching through the RNA-exit channel to connect the N- and C-terminal domains. The holoenzyme structure provides insight into the structural organization of transcription intermediate complexes and into the mechanism of transcription initiation.

Crystal structure of a bacterial RNA polymerase holoenzyme at 2.6 A resolution., Vassylyev DG, Sekine S, Laptenko O, Lee J, Vassylyeva MN, Borukhov S, Yokoyama S, Nature. 2002 Jun 13;417(6890):712-9. Epub 2002 May 8. PMID:12000971

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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Categories: Catabolite Activator Protein | DNA-directed RNA polymerase | Thermus thermophilus | RSGI, RIKEN Structural Genomics/Proteomics Initiative. | Riken structural genomics/proteomics initiative | Rna polymerase holoenzyme | Rsgi | Structural genomic