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Nature. 2002 Nov 7;420(6911):43-50. Epub 2002 Oct 9.

Structure of a T7 RNA polymerase elongation complex at 2.9 A resolution.

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  • 1High Throughput Factory, RIKEN Harima Institute at SPring-8, 1-1-1 Kouto, Mikazuki-cho, Sayo, Hyogo 679-5148, Japan.


The single-subunit bacteriophage T7 RNA polymerase carries out the transcription cycle in an identical manner to that of bacterial and eukaryotic multisubunit enzymes. Here we report the crystal structure of a T7 RNA polymerase elongation complex, which shows that incorporation of an 8-base-pair RNA-DNA hybrid into the active site of the enzyme induces a marked rearrangement of the amino-terminal domain. This rearrangement involves alternative folding of about 130 residues and a marked reorientation (about 130 degrees rotation) of a stable core subdomain, resulting in a structure that provides elements required for stable transcription elongation. A wide opening on the enzyme surface that is probably an RNA exit pathway is formed, and the RNA-DNA hybrid is completely buried in a newly formed, deep protein cavity. Binding of 10 base pairs of downstream DNA is stabilized mostly by long-distance electrostatic interactions. The structure implies plausible mechanisms for the various phases of the transcription cycle, and reveals important structural similarities with the multisubunit RNA polymerases.

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