1IW7:
reference: 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. PMID: 12000971

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