View source for 6n21


==Structure of wild-type CAO1==
<StructureSection load='6n21' size='340' side='right'caption='[[6n21]], [[Resolution|resolution]] 2.04&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[6n21]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Neurospora_crassa Neurospora crassa]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6N21 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6N21 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]] 2.04&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CL:CHLORIDE+ION'>CL</scene>, <scene name='pdbligand=FE2:FE+(II)+ION'>FE2</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=6n21 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6n21 OCA], [https://pdbe.org/6n21 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6n21 RCSB], [https://www.ebi.ac.uk/pdbsum/6n21 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6n21 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/A0A0B0DIC8_NEUCS A0A0B0DIC8_NEUCS] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Carotenoid cleavage dioxygenases (CCDs) use a non-heme Fe(II) cofactor to split alkene bonds of carotenoid and stilbenoid substrates. The iron centers of CCDs are typically five-coordinate in their resting states, with solvent occupying an exchangeable site. The involvement of this iron-bound solvent in CCD catalysis has not been experimentally addressed, but computational studies suggest two possible roles: 1) solvent dissociation provides a coordination site for O2, or 2) solvent remains bound to iron but changes its equilibrium position to allow O2 binding and potentially acts as a proton source. To test these predictions, we investigated isotope effects (H2O versus D2O) on two stilbenoid-cleaving CCDs, Novosphingobium aromaticivorans oxygenase 2 (NOV2) and Neurospora crassa carotenoid oxygenase 1 (CAO1), using piceatannol as a substrate. NOV2 exhibited an inverse isotope effect (kH/kD ~0.6) in an air-saturated buffer, suggesting that solvent dissociates from iron during the catalytic cycle. By contrast, CAO1 displayed a normal isotope effect (kH/kD ~1.7) suggesting proton transfer in the rate-limiting step. X-ray absorption spectroscopy on NOV2 and CAO1 indicated that the protonation states of the iron ligands are unchanged within the pH 6.5-8.5 and that the Fe(II)-aquo bond is minimally altered by substrate binding. We pinpointed the origin of the differential kinetic behaviors of NOV2 and CAO1 to a single amino acid difference near the solvent-binding site of iron, and X-ray crystallography revealed that the substitution alters binding of diffusible ligand to the iron center. We conclude that solvent-iron dissociation and proton transfer are both associated with the CCD catalytic mechanism.

Evidence for distinct rate-limiting steps in the cleavage of alkenes by carotenoid cleavage dioxygenases.,Khadka N, Farquhar ER, Hill HE, Shi W, von Lintig J, Kiser PD J Biol Chem. 2019 May 28. pii: RA119.007535. doi: 10.1074/jbc.RA119.007535. PMID:31138651<ref>PMID:31138651</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 6n21" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Neurospora crassa]]
[[Category: Khadka N]]
[[Category: Kiser PD]]