Database accession: MF7000852
Name: RbcX (Anabaena sp. CA = ATCC 33047)
PDB ID: 2peq
Experimental method: X-ray (1.90 Å)
Assembly: Homodimer
Source organism: Picosynechococcus sp
Primary publication of the structure:
Saschenbrecker S, Bracher A, Rao KV, Rao BV, Hartl FU, Hayer-Hartl M
Structure and function of RbcX, an assembly chaperone for hexadecameric Rubisco.
(2007) Cell 129: 1189-200
PMID: 17574029
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.
Annotations from the GeneOntology database. Only terms that fit at least two of the interacting proteins are shown. Molecular function:
protein folding chaperone protein folding chaperone
protein homodimerization activity protein homodimerization activity
Biological process:
carbon fixation carbon fixation
photosynthesis photosynthesis
ribulose bisphosphate carboxylase complex assembly ribulose bisphosphate carboxylase complex assembly
Cellular component:
carboxysome carboxysome
cytoplasm cytoplasm
Structural annotations of the participating protein chains.Entry contents: 2 distinct polypeptide molecules
Chains: A, B
Notes: All chains according to the most probable oligomerization state stored in PDBe were considered.
Number of unique protein segments: 1
Name: RuBisCO chaperone RbcX
Source organism: Picosynechococcus sp
Length: 134 residues
Sequence:Sequence according to the corresponding UniProt protein segmentMEFKKVAKETAITLQSYLTYQAVRLISQQLSETNPGQAIWLGEFSKRHPIQESDLYLEAMMLENKELVLRILTVRENLAEGVLEFLPEMVLSQIKQSNGNHRRSLLERLTQVDSSSTDQTEPNPGESDTSEDSE
UniProtKB AC: Q44177 (positions: 1-109)
Coverage: 81%
Name: RuBisCO chaperone RbcX
Source organism: Picosynechococcus sp
Length: 134 residues
Sequence:Sequence according to the corresponding UniProt protein segmentMEFKKVAKETAITLQSYLTYQAVRLISQQLSETNPGQAIWLGEFSKRHPIQESDLYLEAMMLENKELVLRILTVRENLAEGVLEFLPEMVLSQIKQSNGNHRRSLLERLTQVDSSSTDQTEPNPGESDTSEDSE
UniProtKB AC: Q44177 (positions: 1-109)
Coverage: 81%
Evidence demonstrating that the participating proteins are unstructured prior to the interaction and their folding is coupled to binding. Representative domain in related structures: Chaperonin-like RbcX
Evidence level: Indirect evidence
Evidence coverage: The full structure participates in mutual synergistic folding.
Complex Evidence:
There is no information on the stability/disoder of the monomeric forms. However, RbcX is a dimer in solution (PMID:17574029) and its biologically relevant form is the homodimer (a monomeric form with this fold is not known PMID:23295968, PMID:21821880). The structure is highly intertwined with the interface being extended and hydrophobic between the two four-helix-bundle cores and by the exchange of the C-terminal parts of the long a4 helices between the two subunits (PMID:21821880).
Chain A:
N/A
Chain B:
N/A
Surface and contacts features:
Structures from the PDB that contain the same number of proteins, and the proteins from the two structures show a sufficient degree of pairwise similarity, i.e. they belong to the same UniRef90 cluster (the full proteins exhibit at least 90% sequence identity) and convey roughly the same region to their respective interactions (the two regions from the two proteins share a minimum of 70% overlap). Download the CIF file (.cif)
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