3hyb
Crystal structure of RbcX from Anabaena, crystal form II
Structural highlights
FunctionRBCX_ANASC An RbcL-specific chaperone. The central cleft of the RbcX homodimer (RbcX2) binds the C-terminus of an RbcL monomer, stabilizing the C-terminus and probably preventing its reassociation with chaperonin GroEL-ES. At the same time the peripheral region of RbcX2 binds a second RbcL monomer, bridging the RbcL homodimers in the correct orientation. The RbcX2(2)-bound RbcL dimers then assemble into the RbcL8 core (RbcL8-(RbcX2)8). RbcS binding triggers the release of RbcX2 (PubMed:20075914, PubMed:21765418).[HAMAP-Rule:MF_00855][1] [2] Required for optimal reconstitution of RuBisCO upon expression of rbcL-rbcS subunits in E.coli (PubMed:9171433).[3] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedForm I Rubisco (ribulose 1,5-bisphosphate carboxylase/oxygenase), a complex of eight large (RbcL) and eight small (RbcS) subunits, catalyses the fixation of atmospheric CO(2) in photosynthesis. The limited catalytic efficiency of Rubisco has sparked extensive efforts to re-engineer the enzyme with the goal of enhancing agricultural productivity. To facilitate such efforts we analysed the formation of cyanobacterial form I Rubisco by in vitro reconstitution and cryo-electron microscopy. We show that RbcL subunit folding by the GroEL/GroES chaperonin is tightly coupled with assembly mediated by the chaperone RbcX(2). RbcL monomers remain partially unstable and retain high affinity for GroEL until captured by RbcX(2). As revealed by the structure of a RbcL(8)-(RbcX(2))(8) assembly intermediate, RbcX(2) acts as a molecular staple in stabilizing the RbcL subunits as dimers and facilitates RbcL(8) core assembly. Finally, addition of RbcS results in RbcX(2) release and holoenzyme formation. Specific assembly chaperones may be required more generally in the formation of complex oligomeric structures when folding is closely coupled to assembly. Coupled chaperone action in folding and assembly of hexadecameric Rubisco.,Liu C, Young AL, Starling-Windhof A, Bracher A, Saschenbrecker S, Rao BV, Rao KV, Berninghausen O, Mielke T, Hartl FU, Beckmann R, Hayer-Hartl M Nature. 2010 Jan 14;463(7278):197-202. PMID:20075914[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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