View source for 6tyg


==Crystal structure of MTB sigma L transcription initiation complex with 9 nt long RNA primer==
<StructureSection load='6tyg' size='340' side='right'caption='[[6tyg]], [[Resolution|resolution]] 3.50&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[6tyg]] is a 9 chain structure with sequence from [https://en.wikipedia.org/wiki/Mycobacterium_tuberculosis Mycobacterium tuberculosis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6TYG OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6TYG 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]] 3.5&#8491;</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=6tyg FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6tyg OCA], [https://pdbe.org/6tyg PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6tyg RCSB], [https://www.ebi.ac.uk/pdbsum/6tyg PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6tyg ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/SIGL_MYCTU 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.<ref>PMID:16199577</ref> <ref>PMID:16552079</ref> 
<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 6tyg" 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: Mycobacterium tuberculosis]]
[[Category: Ebright RH]]
[[Category: Molodtsov V]]