View source for 4am3


==Crystal structure of C. crescentus PNPase bound to RNA==
<StructureSection load='4am3' size='340' side='right' caption='[[4am3]], [[Resolution|resolution]] 3.00&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4am3]] is a 7 chain structure with sequence from [http://en.wikipedia.org/wiki/Caucr Caucr] and [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4AM3 OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=4AM3 FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=PO4:PHOSPHATE+ION'>PO4</scene></td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[4aid|4aid]], [[4aim|4aim]]</td></tr>
<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Polyribonucleotide_nucleotidyltransferase Polyribonucleotide nucleotidyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.7.7.8 2.7.7.8] </span></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=4am3 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4am3 OCA], [http://pdbe.org/4am3 PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=4am3 RCSB], [http://www.ebi.ac.uk/pdbsum/4am3 PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=4am3 ProSAT]</span></td></tr>
</table>
== Function ==
[[http://www.uniprot.org/uniprot/PNP_CAUCR PNP_CAUCR]] Involved in mRNA degradation. Catalyzes the phosphorolysis of single-stranded polyribonucleotides processively in the 3'- to 5'-direction (By similarity). 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Polynucleotide phosphorylase (PNPase) is an exoribonuclease that cleaves single-stranded RNA substrates with 3'-5' directionality and processive behaviour. Its ring-like, trimeric architecture creates a central channel where phosphorolytic active sites reside. One face of the ring is decorated with RNA-binding K-homology (KH) and S1 domains, but exactly how these domains help to direct the 3' end of single-stranded RNA substrates towards the active sites is an unsolved puzzle. Insight into this process is provided by our crystal structures of RNA-bound and apo Caulobacter crescentus PNPase. In the RNA-free form, the S1 domains adopt a 'splayed' conformation that may facilitate capture of RNA substrates. In the RNA-bound structure, the three KH domains collectively close upon the RNA and direct the 3' end towards a constricted aperture at the entrance of the central channel. The KH domains make non-equivalent interactions with the RNA, and there is a marked asymmetry within the catalytic core of the enzyme. On the basis of these data, we propose that structural non-equivalence, induced upon RNA binding, helps to channel substrate to the active sites through mechanical ratcheting. Structural and biochemical analyses also reveal the basis for PNPase association with RNase E in the multi-enzyme RNA degradosome assembly of the alpha-proteobacteria.

Crystal structure of Caulobacter crescentus polynucleotide phosphorylase reveals a mechanism of RNA substrate channelling and RNA degradosome assembly.,Hardwick SW, Gubbey T, Hug I, Jenal U, Luisi BF Open Biol. 2012 Apr;2(4):120028. PMID:22724061<ref>PMID:22724061</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 4am3" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Caucr]]
[[Category: Escherichia coli]]
[[Category: Polyribonucleotide nucleotidyltransferase]]
[[Category: Gubbey, T]]
[[Category: Hardwick, S W]]
[[Category: Hug, I]]
[[Category: Jenal, U]]
[[Category: Luisi, B F]]
[[Category: Kh domain]]
[[Category: Rnase e]]
[[Category: Transferase-rna complex]]