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==Thermus thermophilus initial transcription complex comprising sigma A and 5'-triphosphate RNA of 4 nt==
<StructureSection load='6kql' size='340' side='right'caption='[[6kql]], [[Resolution|resolution]] 2.89&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[6kql]] is a 9 chain structure with sequence from [https://en.wikipedia.org/wiki/Thermus_thermophilus_HB8 Thermus thermophilus HB8] and [https://en.wikipedia.org/wiki/Synthetic_construct Synthetic construct]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6KQL OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6KQL FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.89&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=MG:MAGNESIUM+ION'>MG</scene>, <scene name='pdbligand=UTP:URIDINE+5-TRIPHOSPHATE'>UTP</scene>, <scene name='pdbligand=ZN:ZINC+ION'>ZN</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=6kql FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6kql OCA], [https://pdbe.org/6kql PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6kql RCSB], [https://www.ebi.ac.uk/pdbsum/6kql PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6kql ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/RPOB_THET8 RPOB_THET8] DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates.
<div style="background-color:#fffaf0;">
== 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<ref>PMID:32127479</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 6kql" style="background-color:#fffaf0;"></div>

==See Also==
*[[RNA polymerase 3D structures|RNA polymerase 3D structures]]
*[[Sigma factor 3D structures|Sigma factor 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Synthetic construct]]
[[Category: Thermus thermophilus HB8]]
[[Category: Ebright RH]]
[[Category: Li L]]
[[Category: Zhang Y]]