6pig

==VC-Tn6677 multisubunit CRISPR/Cas effector, open conformation.==

<StructureSection load='6pig' size='340' side='right'caption='[[6pig]], [[Resolution|resolution]] 3.50&Aring;' scene=''>

<table><tr><td colspan='2'>[[6pig]] is a 11 chain structure with sequence from [http://en.wikipedia.org/wiki/"bacillo_virgola_del_koch"_trevisan_1884 "bacillo virgola del koch" trevisan 1884]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6PIG OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=6PIG FirstGlance]. <br>

</td></tr><tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=6pig FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6pig OCA], [http://pdbe.org/6pig PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=6pig RCSB], [http://www.ebi.ac.uk/pdbsum/6pig PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=6pig ProSAT]</span></td></tr>

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== Publication Abstract from PubMed ==

Bacteria use adaptive immune systems encoded by CRISPR and Cas genes to maintain genomic integrity when challenged by pathogens and mobile genetic elements(1-3). Type I CRISPR-Cas systems typically target foreign DNA for degradation via joint action of the ribonucleoprotein complex Cascade and the helicase-nuclease Cas3(4,5), but nuclease-deficient type I systems lacking Cas3 have been repurposed for RNA-guided transposition by bacterial Tn7-like transposons(6,7). How CRISPR- and transposon-associated machineries collaborate during DNA targeting and insertion remains unknown. Here we describe structures of a TniQ-Cascade complex encoded by the Vibrio cholerae Tn6677 transposon using cryo-electron microscopy, revealing the mechanistic basis of this functional coupling. The cryo-electron microscopy maps enabled de novo modelling and refinement of the transposition protein TniQ, which binds to the Cascade complex as a dimer in a head-to-tail configuration, at the interface formed by Cas6 and Cas7 near the 3' end of the CRISPR RNA (crRNA). The natural Cas8-Cas5 fusion protein binds the 5' crRNA handle and contacts the TniQ dimer via a flexible insertion domain. A target DNA-bound structure reveals critical interactions necessary for protospacer-adjacent motif recognition and R-loop formation. This work lays the foundation for a structural understanding of how DNA targeting by TniQ-Cascade leads to downstream recruitment of additional transposase proteins, and will guide protein engineering efforts to leverage this system for programmable DNA insertions in genome-engineering applications.

 

== References ==

</StructureSection>

[[Category: Halpin-Healy, T]]

[[Category: Klompe, S]]

[[Category: Stemberg, S]]

[[Category: Cascade]]

[[Category: Rna binding protein-rna complex]]