View source for 9eeo


==Cryo-EM model of E. coli aspartate transcarbamoylase in the R-state complexed with CP, succinate, CTP, and Mg2+==
<StructureSection load='9eeo' size='340' side='right'caption='[[9eeo]], [[Resolution|resolution]] 3.53&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[9eeo]] is a 12 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=9EEO OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=9EEO 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]] 3.53&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CP:PHOSPHORIC+ACID+MONO(FORMAMIDE)ESTER'>CP</scene>, <scene name='pdbligand=CTP:CYTIDINE-5-TRIPHOSPHATE'>CTP</scene>, <scene name='pdbligand=MG:MAGNESIUM+ION'>MG</scene>, <scene name='pdbligand=SIN:SUCCINIC+ACID'>SIN</scene>, <scene name='pdbligand=ZN:ZINC+ION'>ZN</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=9eeo FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=9eeo OCA], [https://pdbe.org/9eeo PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=9eeo RCSB], [https://www.ebi.ac.uk/pdbsum/9eeo PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=9eeo ProSAT]</span></td></tr>
</table>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Aspartate transcarbamoylase (ATCase) from Escherichia coli catalyzes a key step in pyrimidine nucleotide biosynthesis and has long served as a model for allosteric regulation. Despite decades of study, how nucleotide binding at distant regulatory sites controls cooperativity between active sites remained unresolved. Here we show that ATCase does not simply interconvert between two conformations, as traditionally depicted, but instead samples a continuum of conformations that tune enzyme cooperativity. Using complementary cryo-electron microscopy, small-angle X-ray scattering, and crystallography under conditions that ensure full assembly of the allosteric sites, we show that ATCase behaves like a flexible balloon whose global "breathing" motions directly regulate activity: compression enforces high cooperativity, inhibiting the enzyme, whereas expansion relieves this cooperativity and activates the enzyme. We further show that all four ribonucleoside triphosphates act in symmetric pairs to tune this motion, with the pyrimidines CTP and UTP compressing the enzyme to limit further pyrimidine production, and the purines ATP and GTP expanding it to balance pyrimidine and purine pools. Together, these findings uncover a dynamic breathing mechanism for long-range allosteric communication in ATCase.

Cooperativity in E. coli aspartate transcarbamoylase is tuned by allosteric breathing.,Miller RC, Patterson MG, Bhatt N, Pei X, Ando N Nat Commun. 2026 Mar 20. doi: 10.1038/s41467-026-70909-y. PMID:41862478<ref>PMID:41862478</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 9eeo" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Escherichia coli]]
[[Category: Large Structures]]
[[Category: Ando N]]
[[Category: Miller RC]]
[[Category: Patterson MG]]