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==Crystal structure of GDP-form protofilaments of Bacillus thuringiensis serovar israelensis TubZ==
<StructureSection load='2xkb' size='340' side='right'caption='[[2xkb]], [[Resolution|resolution]] 3.00&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2xkb]] is a 12 chain structure with sequence from [https://en.wikipedia.org/wiki/Bacillus_thuringiensis_serovar_israelensis Bacillus thuringiensis serovar israelensis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2XKB OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2XKB 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]] 3&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=GDP:GUANOSINE-5-DIPHOSPHATE'>GDP</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=2xkb FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2xkb OCA], [https://pdbe.org/2xkb PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2xkb RCSB], [https://www.ebi.ac.uk/pdbsum/2xkb PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2xkb ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/TUBZ_BACTI TUBZ_BACTI] A tubulin-like, filament forming GTPase; the motor component of the type III plasmid partition system which ensures correct segregation of the pBtoxis plasmid. Filaments may seed from the centromere-like site (tubC) when bound by DNA-binding protein TubR; the tubC-TubR complex stabilizes the TubZ filament. Filaments grow at the plus end and depolymerize at the minus end, a process called treadmilling. TubR-tubC complexes track the depolymerizing minus end of the filament, probably pulling plasmid within the cell (PubMed:20534443, PubMed:23010931, PubMed:25825718). Required for pBtoxis plasmid replication/partition (PubMed:16936050, PubMed:17873046). Binds the TubR-tubC complex; GTP is not required for binding to TubR-tubC. TubZ alone does not bind DNA (PubMed:17873046, PubMed:20534443, PubMed:25825718). Has a high GTPase activity in the presence of Mg(2+); in the presence of GTP assembles into dynamic filaments which upon polymerization bind almost exclusively GDP. Filament formation is cooperative, requiring a critical concentration. Formation occurs very quickly and is followed by disassembly as GTP is consumed (PubMed:18198178).<ref>PMID:16936050</ref> <ref>PMID:17873046</ref> <ref>PMID:18198178</ref> <ref>PMID:20534443</ref> <ref>PMID:23010931</ref> <ref>PMID:25825718</ref> 
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== Publication Abstract from PubMed ==
Low copy number plasmids often depend on accurate partitioning systems for their continued survival. Generally, such systems consist of a centromere-like region of DNA, a DNA-binding adaptor, and a polymerizing cytomotive filament. Together these components drive newly replicated plasmids to opposite ends of the dividing cell. The Bacillus thuringiensis plasmid pBToxis relies on a filament of the tubulin/FtsZ-like protein TubZ for its segregation. By combining crystallography and electron microscopy, we have determined the structure of this filament. We explain how GTP hydrolysis weakens the subunit-subunit contact and also shed light on the partitioning of the plasmid-adaptor complex. The double helical superstructure of TubZ filaments is unusual for tubulin-like proteins. Filaments of ParM, the actin-like partitioning protein, are also double helical. We suggest that convergent evolution shapes these different types of cytomotive filaments toward a general mechanism for plasmid separation.

Filament structure of bacterial tubulin homologue TubZ.,Aylett CH, Wang Q, Michie KA, Amos LA, Lowe J Proc Natl Acad Sci U S A. 2010 Oct 25. PMID:20974911<ref>PMID:20974911</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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== References ==
<references/>
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</StructureSection>
[[Category: Bacillus thuringiensis serovar israelensis]]
[[Category: Large Structures]]
[[Category: Aylett CHS]]
[[Category: Lowe J]]