5tjg
From Proteopedia
Thermus aquaticus delta1.1-sigmaA holoenzyme/downstream-fork promoter complex with an open clamp
Structural highlights
Function[RPOZ_THEAQ] Promotes RNA polymerase assembly. Latches the N- and C-terminal regions of the beta' subunit thereby facilitating its interaction with the beta and alpha subunits.[1] [SIGA_THEAQ] Sigma factors are initiation factors that promote the attachment of RNA polymerase to specific initiation sites and are then released. This sigma factor is the primary sigma factor during exponential growth.[HAMAP-Rule:MF_00963][2] [3] Publication Abstract from PubMedAll cellular RNA polymerases (RNAPs), from those of bacteria to those of man, possess a clamp that can open and close, and it has been assumed that the open RNAP separates promoter DNA strands and then closes to establish a tight grip on the DNA template. Here, we resolve successive motions of the initiating bacterial RNAP by studying real-time signatures of fluorescent reporters placed on RNAP and DNA in the presence of ligands locking the clamp in distinct conformations. We report evidence for an unexpected and obligatory step early in the initiation involving a transient clamp closure as a prerequisite for DNA melting. We also present a 2.6-angstrom crystal structure of a late-initiation intermediate harboring a rotationally unconstrained downstream DNA duplex within the open RNAP active site cleft. Our findings explain how RNAP thermal motions control the promoter search and drive DNA melting in the absence of external energy sources. RNA polymerase motions during promoter melting.,Feklistov A, Bae B, Hauver J, Lass-Napiorkowska A, Kalesse M, Glaus F, Altmann KH, Heyduk T, Landick R, Darst SA Science. 2017 May 26;356(6340):863-866. doi: 10.1126/science.aam7858. PMID:28546214[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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