9w00

Crystal structure of C-terminal domain of theta type Carbonic Anhydrase 3 from marine diatom Phaeodactylum tricornutum

spinqualitylabelsall models 9w00, resolution 1.50Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 9w00 is a 2 chain structure with sequence from Phaeodactylum tricornutum. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.5Å Ligands: CO2, NA, ZN Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function A0A173M023_PHATR 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 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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