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PDBsum entry 4xix
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PDB id:
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Lyase
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Title:
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Carbonic anhydrase cah3 from chlamydomonas reinhardtii in complex with phosphate.
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Structure:
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Carbonic anhydrase, alpha type. Chain: a, b, c, d, e, f, g, h. Fragment: unp residues 73-310. Synonym: intracellular carbonic anhydrase,alpha type. Engineered: yes
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Source:
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Chlamydomonas reinhardtii. Organism_taxid: 3055. Gene: cah3. Expressed in: escherichia coli. Expression_system_taxid: 562
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Resolution:
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2.70Å
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R-factor:
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0.160
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R-free:
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0.230
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Authors:
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T.Hainzl,C.Grundstrom,R.Benlloch,D.Shevela,T.Shutova,J.Messinger, G.Samuelsson,A.E.Sauer-Eriksson
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Key ref:
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R.Benlloch
et al.
(2015).
Crystal structure and functional characterization of photosystem II-associated carbonic anhydrase CAH3 in Chlamydomonas reinhardtii.
Plant Physiol,
167,
950-962.
PubMed id:
DOI:
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Date:
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08-Jan-15
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Release date:
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11-Feb-15
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PROCHECK
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Headers
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References
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Q39588
(Q39588_CHLRE) -
Carbonic anhydrase from Chlamydomonas reinhardtii
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Seq:
Struc:
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310 a.a.
238 a.a.
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Key: |
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PfamA domain |
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Secondary structure |
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CATH domain |
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Enzyme class:
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E.C.4.2.1.1
- carbonic anhydrase.
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Reaction:
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hydrogencarbonate + H+ = CO2 + H2O
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hydrogencarbonate
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H(+)
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=
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CO2
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+
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H2O
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Cofactor:
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Zn(2+)
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Molecule diagrams generated from .mol files obtained from the
KEGG ftp site
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DOI no:
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Plant Physiol
167:950-962
(2015)
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PubMed id:
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Crystal structure and functional characterization of photosystem II-associated carbonic anhydrase CAH3 in Chlamydomonas reinhardtii.
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R.Benlloch,
D.Shevela,
T.Hainzl,
C.Grundström,
T.Shutova,
J.Messinger,
G.Samuelsson,
A.E.Sauer-Eriksson.
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ABSTRACT
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In oxygenic photosynthesis, light energy is stored in the form of chemical
energy by converting CO2 and water into carbohydrates. The light-driven
oxidation of water that provides the electrons and protons for the subsequent
CO2 fixation takes place in photosystem II (PSII). Recent studies show that in
higher plants, HCO3 (-) increases PSII activity by acting as a mobile acceptor
of the protons produced by PSII. In the green alga Chlamydomonas reinhardtii, a
luminal carbonic anhydrase, CrCAH3, was suggested to improve proton removal from
PSII, possibly by rapid reformation of HCO3 (-) from CO2. In this study, we
investigated the interplay between PSII and CrCAH3 by membrane inlet mass
spectrometry and x-ray crystallography. Membrane inlet mass spectrometry
measurements showed that CrCAH3 was most active at the slightly acidic pH values
prevalent in the thylakoid lumen under illumination. Two crystal structures of
CrCAH3 in complex with either acetazolamide or phosphate ions were determined at
2.6- and 2.7-Å resolution, respectively. CrCAH3 is a dimer at pH 4.1 that is
stabilized by swapping of the N-terminal arms, a feature not previously observed
in α-type carbonic anhydrases. The structure contains a disulfide bond, and
redox titration of CrCAH3 function with dithiothreitol suggested a possible
redox regulation of the enzyme. The stimulating effect of CrCAH3 and CO2/HCO3
(-) on PSII activity was demonstrated by comparing the flash-induced oxygen
evolution pattern of wild-type and CrCAH3-less PSII preparations. We showed that
CrCAH3 has unique structural features that allow this enzyme to maximize PSII
activity at low pH and CO2 concentration.
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