2PEO: Crystal Structure Of Rbcx From Anabaena Ca

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.
PDB ID: 2PEODownload
MMDB ID: 47483
PDB Deposition Date: 2007/4/3
Updated in MMDB: 2007/11
Experimental Method:
x-ray diffraction
Resolution: 2.5  Å
Source Organism:
Similar Structures:
Biological Unit for 2PEO: dimeric; determined by author and by software (PISA)
Molecular Components in 2PEO
Label Count Molecule
Proteins (2 molecules)
Rbcx Protein
Molecule annotation
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Citing MMDB