View source for 8dzt


==Crystal structure of human Sar1aH79G mutant==
<StructureSection load='8dzt' size='340' side='right'caption='[[8dzt]], [[Resolution|resolution]] 1.80&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[8dzt]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=8DZT OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=8DZT 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]] 1.8&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=G4P:GUANOSINE-5,3-TETRAPHOSPHATE'>G4P</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=8dzt FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=8dzt OCA], [https://pdbe.org/8dzt PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=8dzt RCSB], [https://www.ebi.ac.uk/pdbsum/8dzt PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=8dzt ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/SAR1A_HUMAN SAR1A_HUMAN] Involved in transport from the endoplasmic reticulum to the Golgi apparatus (By similarity). Required to maintain SEC16A localization at discrete locations on the ER membrane perhaps by preventing its dissociation. SAR1A-GTP-dependent assembly of SEC16A on the ER membrane forms an organized scaffold defining endoplasmic reticulum exit sites (ERES).<ref>PMID:17005010</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Transport of newly synthesized proteins from endoplasmic reticulum (ER) to Golgi is mediated by coat protein complex II (COPII). The assembly and disassembly of COPII vesicles is regulated by the molecular switch Sar1, which is a small GTPase and a component of COPII. Usually a small GTPase binds GDP (inactive form) or GTP (active form). Mammals have two Sar1 isoforms, Sar1a and Sar1b, that have approximately 90% sequence identity. Some experiments demonstrated that these two isoforms had distinct but overlapping functions. Here we found another instance of differing behavior: the alarmone ppGpp could bind to and inhibit the GTPase activity of human Sar1a but could not inhibit the GTPase activity of human Sar1b. The crystal structures of Sar1aâppGpp and Sar1bâGDP have been determined. Superposition of the structures shows that ppGpp binds to the nucleotide-binding pocket, its guanosine base, ribose ring and 5'-diphosphate occupying nearly the same positions as for GDP. However, its 3'-diphosphate points away from the active site and, hence, away from the surface of the protein. The overall structure of Sar1aâppGpp is more similar to Sar1bâGDP than to Sar1bâGTP. We also find that the Asp140-Arg138-water-ligand interaction net is important for the binding of ppGpp to Sar1a. This study provides further evidence showing that there are biochemical differences between the Sar1a and Sar1b isoforms of Sar1.

The alarmone ppGpp selectively inhibits the isoform A of the human small GTPase Sar1.,Huang Q, Szebenyi DME Proteins. 2022 Nov 11. doi: 10.1002/prot.26445. PMID:36369712<ref>PMID:36369712</ref>

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

==See Also==
*[[GTP-binding protein 3D structures|GTP-binding protein 3D structures]]
== References ==
<references/>
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</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Huang Q]]