Tracking RNA polymerase, one step at a time

Although the structural analysis of transcription has attained atomic resolution, techniques to manipulate single molecules involved in transcription have lagged behind. A recent paper in Nature by Abbondanzieri et al. (2005) closes this gap. This study finds that individual molecules of bacterial RNA polymerase move in single base-pair steps and concludes that RNA polymerase acts as a Brownian ratchet that is driven forward by the binding of incoming nucleoside triphosphates.