Crystal structure of RbcX in complex with substrate

Experimental Data Snapshot

  • Resolution: 2.95 Å
  • R-Value Free: 0.264 
  • R-Value Work: 0.235 
  • R-Value Observed: 0.236 

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Structure and Function of RbcX, an Assembly Chaperone for Hexadecameric Rubisco.

Saschenbrecker, S.Bracher, A.Rao, K.V.Rao, B.V.Hartl, F.U.Hayer-Hartl, M.

(2007) Cell 129: 1189-1200

  • DOI: https://doi.org/10.1016/j.cell.2007.04.025
  • Primary Citation of Related Structures:  
    2PEI, 2PEJ, 2PEK, 2PEM, 2PEN, 2PEO, 2PEQ

  • PubMed Abstract: 

    After folding, many proteins must assemble into oligomeric complexes to become biologically active. Here we describe the role of RbcX as an assembly chaperone of ribulose-bisphosphate carboxylase/oxygenase (Rubisco), the enzyme responsible for the fixation of atmospheric carbon dioxide. In cyanobacteria and plants, Rubisco is an approximately 520 kDa complex composed of eight large subunits (RbcL) and eight small subunits (RbcS). We found that cyanobacterial RbcX functions downstream of chaperonin-mediated RbcL folding in promoting the formation of RbcL(8) core complexes. Structural analysis revealed that the 15 kDa RbcX forms a homodimer with two cooperating RbcL-binding regions. A central cleft specifically binds the exposed C-terminal peptide of RbcL subunits, enabling a peripheral surface of RbcX to mediate RbcL(8) assembly. Due to the dynamic nature of these interactions, RbcX is readily displaced from RbcL(8) complexes by RbcS, producing the active enzyme. The strategies employed by RbcX in achieving substrate specificity and efficient product release may be generally relevant in assisted assembly reactions.

  • 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
A, B, C, D, E
A, B, C, D, E, F
134Picosynechococcus sp. PCC 7002Mutation(s): 0 
Gene Names: rbcXorf134SYNPCC7002_A1797
Find proteins for Q44177 (Synechococcus sp. (strain ATCC 27264 / PCC 7002 / PR-6))
Explore Q44177 
Go to UniProtKB:  Q44177
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ44177
Sequence Annotations
  • Reference Sequence

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Entity ID: 2
MoleculeChains Sequence LengthOrganismDetailsImage
RbcLG [auth R]7N/AMutation(s): 0 
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.95 Å
  • R-Value Free: 0.264 
  • R-Value Work: 0.235 
  • R-Value Observed: 0.236 
  • Space Group: P 41 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 93.207α = 90
b = 93.207β = 90
c = 412.016γ = 90
Software Package:
Software NamePurpose
SCALAdata scaling
PDB_EXTRACTdata extraction
ADSCdata collection
MOSFLMdata reduction

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2007-07-10
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Source and taxonomy, Version format compliance
  • Version 1.3: 2023-08-30
    Changes: Data collection, Database references, Refinement description