Carbonic anhydrase Cah3 from Chlamydomonas reinhardtii in complex with phosphate.

Experimental Data Snapshot

  • Resolution: 2.70 Å
  • R-Value Free: 0.230 
  • R-Value Work: 0.156 
  • R-Value Observed: 0.160 

wwPDB Validation   3D Report Full Report

This is version 2.1 of the entry. See complete history


Crystal Structure and Functional Characterization of Photosystem II-Associated Carbonic Anhydrase CAH3 in Chlamydomonas reinhardtii.

Benlloch, R.Shevela, D.Hainzl, T.Grundstrom, C.Shutova, T.Messinger, J.Samuelsson, G.Sauer-Eriksson, A.E.

(2015) Plant Physiol 167: 950-962

  • DOI: https://doi.org/10.1104/pp.114.253591
  • Primary Citation of Related Structures:  
    4XIW, 4XIX

  • PubMed Abstract: 

    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.

  • Organizational Affiliation

    Department of Forest Genetics and Plant Physiology (R.B) and Department of Plant Physiology (T.S., G.S.), Umeå Plant Science Centre, and Department of Chemistry, Chemistry Biology Centre (D.S., T.H., C.G., J.M., A.E.S.-E.), Umeå University, SE-90187 Umea, Sweden.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Carbonic anhydrase, alpha type
A, B, C, D, E
A, B, C, D, E, F, G, H
239Chlamydomonas reinhardtiiMutation(s): 0 
Gene Names: CAH3
Find proteins for Q39588 (Chlamydomonas reinhardtii)
Explore Q39588 
Go to UniProtKB:  Q39588
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ39588
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on 2HP

Download Ideal Coordinates CCD File 
AA [auth E]
BA [auth E]
CA [auth E]
EA [auth F]
FA [auth F]
AA [auth E],
BA [auth E],
CA [auth E],
EA [auth F],
FA [auth F],
HA [auth G],
IA [auth G],
J [auth A],
K [auth A],
KA [auth H],
L [auth A],
LA [auth H],
M [auth A],
MA [auth H],
NA [auth H],
O [auth B],
P [auth B],
Q [auth B],
S [auth C],
T [auth C],
U [auth C],
V [auth C],
X [auth D],
Y [auth D]
H2 O4 P
Query on ZN

Download Ideal Coordinates CCD File 
DA [auth F]
GA [auth G]
I [auth A]
JA [auth H]
N [auth B]
DA [auth F],
GA [auth G],
I [auth A],
JA [auth H],
N [auth B],
R [auth C],
W [auth D],
Z [auth E]
Experimental Data & Validation

Experimental Data

  • Resolution: 2.70 Å
  • R-Value Free: 0.230 
  • R-Value Work: 0.156 
  • R-Value Observed: 0.160 
  • Space Group: P 32 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 138.957α = 90
b = 138.957β = 90
c = 202.807γ = 120
Software Package:
Software NamePurpose
XDSdata reduction
SCALAdata scaling

Structure Validation

View Full Validation Report

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Swedish Research CouncilSweden--

Revision History  (Full details and data files)

  • Version 1.0: 2015-02-11
    Type: Initial release
  • Version 1.1: 2015-03-11
    Changes: Database references
  • Version 2.0: 2017-09-13
    Changes: Advisory, Atomic model, Author supporting evidence, Derived calculations
  • Version 2.1: 2024-01-10
    Changes: Data collection, Database references, Derived calculations, Refinement description