View source for 9nhe


==Cryo-EM structure of SIWI-piRNA-target(49-nt)-Maelstrom complex==
<StructureSection load='9nhe' size='340' side='right'caption='[[9nhe]], [[Resolution|resolution]] 4.20&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[9nhe]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Bombyx_mori Bombyx mori] 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=9NHE OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=9NHE FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Electron Microscopy, [[Resolution|Resolution]] 4.2&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=A2M:2-O-METHYLADENOSINE+5-(DIHYDROGEN+PHOSPHATE)'>A2M</scene>, <scene name='pdbligand=MG:MAGNESIUM+ION'>MG</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=9nhe FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=9nhe OCA], [https://pdbe.org/9nhe PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=9nhe RCSB], [https://www.ebi.ac.uk/pdbsum/9nhe PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=9nhe ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/SIWI_BOMMO SIWI_BOMMO] Endoribonuclease that plays a central role during spermatogenesis by repressing transposable elements and preventing their mobilization, which is essential for the germline integrity (PubMed:19460866, PubMed:27693359). Plays an essential role in meiotic differentiation of spermatocytes, germ cell differentiation and in self-renewal of spermatogonial stem cells (PubMed:19460866, PubMed:25558067, PubMed:27693359). Its presence in oocytes suggests that it may participate in similar functions during oogenesis in females (PubMed:18191035). Acts via the piRNA metabolic process, which mediates the repression of transposable elements during meiosis by forming complexes composed of piRNAs and Piwi proteins and govern the methylation and subsequent repression of transposons (PubMed:19460866, PubMed:25558067, PubMed:27693359). Directly binds piRNAs, a class of 24 to 30 nucleotide RNAs that are generated by a Dicer-independent mechanism and are primarily derived from transposons and other repeated sequence elements (PubMed:19460866, PubMed:25558067, PubMed:27693359). Recognizes piRNAs containing a phosphate at the 5'-end and a 2'-O-methylation modification at the 3'-end (PubMed:27693359). Strongly prefers a uridine in the first position of their guide (g1U preference, also named 1U-bias) and a complementary adenosine in the target (t1A bias) (PubMed:24757166, PubMed:27693359). Plays a key role in the piRNA amplification loop, also named ping-pong amplification cycle: antisense piRNA-bound Siwi and sense piRNA-bound Ago3 reciprocally cleave complementary transcripts, to couple the amplification of piRNAs with the repression of transposable elements. In this process Siwi acts as a 'slicer-competent' piRNA endoribonuclease that cleaves primary piRNAs, which are then loaded onto Ago3 (PubMed:27693359). In this process, Siwi requires the RNA unwinding activity of the RNA helicase Vasa for the release of the cleavage products (PubMed:25558067).<ref>PMID:18191035</ref> <ref>PMID:19460866</ref> <ref>PMID:24757166</ref> <ref>PMID:25558067</ref> <ref>PMID:27693359</ref> 
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Bombyx mori]]
[[Category: Large Structures]]
[[Category: Synthetic construct]]
[[Category: Gebert LFR]]
[[Category: MacRae IJ]]
[[Category: Sarkar S]]