6tyg

Crystal structure of MTB sigma L transcription initiation complex with 9 nt long RNA primer

spinqualitylabelsall models 6tyg, resolution 3.50Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6tyg is a 9 chain structure with sequence from Mycobacterium tuberculosis. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 3.5Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function SIGL_MYCTU Sigma factors are initiation factors that promote the attachment of RNA polymerase to specific initiation sites and are then released. Extracytoplasmic function (ECF) sigma factors are held in an inactive form by an anti-sigma factor until released by regulated intramembrane proteolysis. Over-expression of SigL induces 19-28 genes including polyketide synthases, secreted and membrane proteins. Might play a minor role in regulating SigB. Publication Abstract from PubMed All organisms-bacteria, archaea, and eukaryotes-have a transcription initiation factor that contains a structural module that binds within the RNA polymerase (RNAP) active-center cleft and interacts with template-strand single-stranded DNA (ssDNA) in the immediate vicinity of the RNAP active center. This transcription initiation-factor structural module preorganizes template-strand ssDNA to engage the RNAP active center, thereby facilitating binding of initiating nucleotides and enabling transcription initiation from initiating mononucleotides. However, this transcription initiation-factor structural module occupies the path of nascent RNA and thus presumably must be displaced before or during initial transcription. Here, we report four sets of crystal structures of bacterial initially transcribing complexes that demonstrate and define details of stepwise, RNA-extension-driven displacement of the "sigma-finger" of the bacterial transcription initiation factor sigma. The structures reveal that-for both the primary sigma-factor and extracytoplasmic (ECF) sigma-factors, and for both 5'-triphosphate RNA and 5'-hydroxy RNA-the "sigma-finger" is displaced in stepwise fashion, progressively folding back upon itself, driven by collision with the RNA 5'-end, upon extension of nascent RNA from approximately 5 nt to approximately 10 nt. RNA extension drives a stepwise displacement of an initiation-factor structural module in initial transcription.,Li L, Molodtsov V, Lin W, Ebright RH, Zhang Y Proc Natl Acad Sci U S A. 2020 Mar 3. pii: 1920747117. doi:, 10.1073/pnas.1920747117. PMID:32127479 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also RNA polymerase 3D structures Sigma factor 3D structures

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