Crystal structure of the AAA+ protein CbbX, native structure

Experimental Data Snapshot

  • Resolution: 3.00 Å
  • R-Value Free: 0.285 
  • R-Value Work: 0.218 
  • R-Value Observed: 0.222 

wwPDB Validation   3D Report Full Report

This is version 1.4 of the entry. See complete history


Structure and function of the AAA+ protein CbbX, a red-type Rubisco activase.

Mueller-Cajar, O.Stotz, M.Wendler, P.Hartl, F.U.Bracher, A.Hayer-Hartl, M.

(2011) Nature 479: 194-199

  • DOI: https://doi.org/10.1038/nature10568
  • Primary Citation of Related Structures:  
    3SYK, 3SYL, 3ZUH

  • PubMed Abstract: 

    Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyses the fixation of atmospheric CO(2) in photosynthesis, but tends to form inactive complexes with its substrate ribulose 1,5-bisphosphate (RuBP). In plants, Rubisco is reactivated by the AAA(+) (ATPases associated with various cellular activities) protein Rubisco activase (Rca), but no such protein is known for the Rubisco of red algae. Here we identify the protein CbbX as an activase of red-type Rubisco. The 3.0-Å crystal structure of unassembled CbbX from Rhodobacter sphaeroides revealed an AAA(+) protein architecture. Electron microscopy and biochemical analysis showed that ATP and RuBP must bind to convert CbbX into functionally active, hexameric rings. The CbbX ATPase is strongly stimulated by RuBP and Rubisco. Mutational analysis suggests that CbbX functions by transiently pulling the carboxy-terminal peptide of the Rubisco large subunit into the hexamer pore, resulting in the release of the inhibitory RuBP. Understanding Rubisco activation may facilitate efforts to improve CO(2) uptake and biomass production by photosynthetic organisms.

  • Organizational Affiliation

    Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Protein CbbX
A, B
309Cereibacter sphaeroidesMutation(s): 1 
Gene Names: cbbXRSKD131_2679
Find proteins for P95648 (Cereibacter sphaeroides)
Explore P95648 
Go to UniProtKB:  P95648
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP95648
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 3.00 Å
  • R-Value Free: 0.285 
  • R-Value Work: 0.218 
  • R-Value Observed: 0.222 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 76.128α = 90
b = 93.141β = 90
c = 106.102γ = 90
Software Package:
Software NamePurpose
SCALAdata scaling
PDB_EXTRACTdata extraction
XDSdata scaling
XDSdata reduction

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2011-11-09
    Type: Initial release
  • Version 1.1: 2011-11-23
    Changes: Database references
  • Version 1.2: 2017-11-08
    Changes: Refinement description
  • Version 1.3: 2019-11-20
    Changes: Database references
  • Version 1.4: 2023-09-13
    Changes: Data collection, Database references, Derived calculations, Refinement description