View source for 9w05


==Crystal structure of C-terminal domain of theta type Carbonic Anhydrase 3 (A88D mutant) from marine diatom Phaeodactylum tricornutum==
<StructureSection load='9w05' size='340' side='right'caption='[[9w05]], [[Resolution|resolution]] 1.64&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[9w05]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Phaeodactylum_tricornutum Phaeodactylum tricornutum]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=9W05 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=9W05 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]] 1.64&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=BCT:BICARBONATE+ION'>BCT</scene>, <scene name='pdbligand=CO2:CARBON+DIOXIDE'>CO2</scene>, <scene name='pdbligand=NA:SODIUM+ION'>NA</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=9w05 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=9w05 OCA], [https://pdbe.org/9w05 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=9w05 RCSB], [https://www.ebi.ac.uk/pdbsum/9w05 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=9w05 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/A0A173M023_PHATR A0A173M023_PHATR] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Carbonic anhydrase (CA) catalyzes the reversible hydration of carbon dioxide (CO(2)) to bicarbonate (HCO(3) (-)) and plays an essential role in carbon fixation in marine diatoms. Here we report the structural and functional characterization of a novel CA, theta-CA3, from the diatom Phaeodactylum tricornutum, elucidating its physiological role and catalytic mechanism. AlphaFold prediction, sequence alignment, and metal analysis showed that theta-CA3 is a dimeric enzyme, with each monomer composed of two zinc-binding catalytic domains. High-resolution X-ray crystallographic structures of domain 2 of theta-CA3 in the CO(2)-bound form revealed the detailed substrate binding pattern in the active site. Site-directed mutagenesis showed that Asp49 and Arg117 in the active site are essential for catalysis. Notably, introducing a negative charge near the active-site entrance resulted in a mutant enzyme with markedly increased activity under acidic pH, suggesting that electrostatic modulation of the active-site environment regulates proton transfer and catalysis. Furthermore, we identified an HCO(3) (-) ion at the dimer interface that contributes to enzyme activation. Collectively, our findings provide fundamental structural insight into how the active-site electrostatic charges and metal environment govern the catalytic efficiency of theta-CA3, offering a new perspective on the molecular basis of carbon fixation in diatoms.

Structural insights into theta-type carbonic anhydrases 3 and 4: Tuning the directionality of CO(2) hydration in a diatom.,Negoro H, Ohsawa A, Shimakawa G, Tanaka H, Matsuda Y, Kurisu G FEBS J. 2026 Jul 14. doi: 10.1111/febs.70654. PMID:42447277<ref>PMID:42447277</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 9w05" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Phaeodactylum tricornutum]]
[[Category: Kurisu G]]
[[Category: Negoro H]]
[[Category: Tanaka H]]