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Curr Opin Struct Biol. 2009 Jun;19(3):294-9. doi: 10.1016/ Epub 2009 May 27.

A movie of the RNA polymerase nucleotide addition cycle.

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Gene Center and Center for Integrated Protein Science Munich (CIPSM), Department of Chemistry and Biochemistry, Ludwig-Maximilians-Universit√§t M√ľnchen, Feodor-Lynen-Strasse 25, 81377 Munich, Germany.


During gene transcription, RNA polymerase (Pol) passes through repetitive cycles of adding a nucleotide to the growing mRNA chain. Here we obtained a movie of the nucleotide addition cycle by combining structural information on different functional states of the Pol II elongation complex (EC). The movie illustrates the two-step loading of the nucleoside triphosphate (NTP) substrate, closure of the active site for catalytic nucleotide incorporation, and the presumed two-step translocation of DNA and RNA, which is accompanied by coordinated conformational changes in the polymerase bridge helix and trigger loop. The movie facilitates teaching and a mechanistic analysis of transcription and can be downloaded from

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