View source for 8cez


==HK97 Portal Protein In situ (prohead II)==
<StructureSection load='8cez' size='340' side='right'caption='[[8cez]], [[Resolution|resolution]] 2.97&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[8cez]] is a 12 chain structure with sequence from [https://en.wikipedia.org/wiki/Hendrixvirus Hendrixvirus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=8CEZ OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=8CEZ 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]] 2.97&#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=8cez FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=8cez OCA], [https://pdbe.org/8cez PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=8cez RCSB], [https://www.ebi.ac.uk/pdbsum/8cez PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=8cez ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/PORTL_BPHK7 PORTL_BPHK7] Forms the portal vertex of the capsid. This portal plays critical roles in head assembly, genome packaging, neck/tail attachment, and genome ejection. The portal protein multimerizes as a single ring-shaped homododecamer arranged around a central channel. Binds to the terminase subunits to form the packaging machine.[UniProtKB:P25480]
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Double-stranded DNA viruses utilise machinery, made of terminase proteins, to package viral DNA into the capsid. For cos bacteriophage, a defined signal, recognised by small terminase, flanks each genome unit. Here we present the first structural data for a cos virus DNA packaging motor, assembled from the bacteriophage HK97 terminase proteins, procapsids encompassing the portal protein, and DNA containing a cos site. The cryo-EM structure is consistent with the packaging termination state adopted after DNA cleavage, with DNA density within the large terminase assembly ending abruptly at the portal protein entrance. Retention of the large terminase complex after cleavage of the short DNA substrate suggests that motor dissociation from the capsid requires headful pressure, in common with pac viruses. Interestingly, the clip domain of the 12-subunit portal protein does not adhere to C12 symmetry, indicating asymmetry induced by binding of the large terminase/DNA. The motor assembly is also highly asymmetric, showing a ring of 5 large terminase monomers, tilted against the portal. Variable degrees of extension between N- and C-terminal domains of individual subunits suggest a mechanism of DNA translocation driven by inter-domain contraction and relaxation.

Insights into a viral motor: the structure of the HK97 packaging termination assembly.,Hawkins DEDP, Bayfield OW, Fung HKH, Grba DN, Huet A, Conway JF, Antson AA Nucleic Acids Res. 2023 Jul 21;51(13):7025-7035. doi: 10.1093/nar/gkad480. PMID:37293963<ref>PMID:37293963</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 8cez" style="background-color:#fffaf0;"></div>

==See Also==
*[[Portal protein 3D structures|Portal protein 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Hendrixvirus]]
[[Category: Large Structures]]
[[Category: Antson AA]]
[[Category: Hawkins DEDP]]