View source for 4al7


==Crystal structure of the Csy4-minimal crRNA complex==
<StructureSection load='4al7' size='340' side='right'caption='[[4al7]], [[Resolution|resolution]] 2.32&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4al7]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Pseudomonas_aeruginosa Pseudomonas aeruginosa]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4AL7 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4AL7 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]] 2.32&#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=4al7 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4al7 OCA], [https://pdbe.org/4al7 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4al7 RCSB], [https://www.ebi.ac.uk/pdbsum/4al7 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4al7 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/CAS6_PSEAB CAS6_PSEAB] CRISPR (clustered regularly interspaced short palindromic repeat) is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain sequences complementary to antecedent mobile elements and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). Processes pre-crRNA into individual crRNA units. Absolutely required for crRNA production or stability. Upon expression in E.coli endonucleolytically processes pre-crRNA, although disruption and reconstitution experiments indicate that in situ other genes are also required for processing. Yields 5'-hydroxy and 3'-phosphate groups. The Csy ribonucleoprotein complex binds target ssDNA with high affinity but target dsDNA with much lower affinity.<ref>PMID:20829488</ref> <ref>PMID:21398535</ref> <ref>PMID:22522703</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
CRISPR-Cas adaptive immune systems protect prokaryotes against foreign genetic elements. crRNAs derived from CRISPR loci base pair with complementary nucleic acids, leading to their destruction. In Pseudomonas aeruginosa, crRNA biogenesis requires the endoribonuclease Csy4, which binds and cleaves the repetitive sequence of the CRISPR transcript. Biochemical assays and three co-crystal structures of wild-type and mutant Csy4/RNA complexes reveal a substrate positioning and cleavage mechanism in which a histidine deprotonates the ribosyl 2'-hydroxyl pinned in place by a serine, leading to nucleophilic attack on the scissile phosphate. The active site catalytic dyad lacks a general acid to protonate the leaving group and positively charged residues to stabilize the transition state, explaining why the observed catalytic rate constant is approximately 10(4)-fold slower than that of RNase A. We show that this RNA cleavage step is essential for assembly of the Csy protein-crRNA complex that facilitates target recognition. Considering that Csy4 recognizes a single cellular substrate and sequesters the cleavage product, evolutionary pressure has likely selected for substrate specificity and high-affinity crRNA interactions at the expense of rapid cleavage kinetics.

Csy4 relies on an unusual catalytic dyad to position and cleave CRISPR RNA.,Haurwitz RE, Sternberg SH, Doudna JA EMBO J. 2012 Apr 20. doi: 10.1038/emboj.2012.107. PMID:22522703<ref>PMID:22522703</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 4al7" style="background-color:#fffaf0;"></div>

==See Also==
*[[CRISPR subtype I-F|CRISPR subtype I-F]]
*[[Endonuclease 3D structures|Endonuclease 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Pseudomonas aeruginosa]]
[[Category: Doudna JA]]
[[Category: Haurwitz RE]]
[[Category: Sternberg SH]]