7xsd

From Proteopedia

Cryo-EM structure of RuBisCO assembly intermediate RbcL8Raf18RbcX16

Structural highlights

7xsd is a 32 chain structure with sequence from Nostoc sp. PCC 7120 = FACHB-418. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	Electron Microscopy, Resolution 3.3Å
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

RBCX_NOSS1 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.[HAMAP-Rule:MF_00855] When rbcL-rbcX-rbcS or rbcL-rbcS were overexpressed in E.coli no change in reconstituted RuBisCO activity was observed, which suggests RbcX plays no role in RuBisCO assembly in this system (PubMed:8472962). However in PubMed:8472962 E.coli chaperones groL and groS were also overexpressed, which may compensate for lack of rbcX (Probable).^[1] ^[2]

Publication Abstract from PubMed

RuBisCO is the most abundant enzyme in nature, catalyzing the fixation of CO(2) in photosynthesis. Its common form consists of eight RbcL and eight RbcS subunits, the assembly of which requires a series of chaperones that include RbcX and RuBisCO accumulation factor 1 (Raf1). To understand how these RuBisCO-specific chaperones function during cyanobacterial RbcL(8)RbcS(8) (L(8)S(8)) holoenzyme formation, we solved a 3.3-A cryo-electron microscopy structure of a 32-subunit RbcL(8)Raf1(8)RbcX(16) (L(8)F(8)X(16)) assembly intermediate from Anabaena sp. PCC 7120. Comparison to the previously resolved L(8)F(8) and L(8)X(16) structures together with biochemical assays revealed that the L(8)F(8)X(16) complex forms a rather dynamic structural intermediate, favoring RbcS displacement of Raf1 and RbcX. In vitro assays further demonstrated that both Raf1 and RbcX function to regulate RuBisCO condensate formation by restricting CcmM35 binding to the stably assembled L(8)S(8) holoenzymes. Combined with previous findings, we propose a model on how Raf1 and RbcX work in concert to facilitate, and regulate, cyanobacterial RuBisCO assembly as well as disassembly of RuBisCO condensates.

Structural insights into cyanobacterial RuBisCO assembly coordinated by two chaperones Raf1 and RbcX.,Li Q, Jiang YL, Xia LY, Chen Y, Zhou CZ Cell Discov. 2022 Sep 20;8(1):93. doi: 10.1038/s41421-022-00436-9. PMID:36123352^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Larimer FW, Soper TS. Overproduction of Anabaena 7120 ribulose-bisphosphate carboxylase/oxygenase in Escherichia coli. Gene. 1993 Apr 15;126(1):85-92. doi: 10.1016/0378-1119(93)90593-r. PMID:8472962 doi:http://dx.doi.org/10.1016/0378-1119(93)90593-r
↑ Onizuka T, Endo S, Akiyama H, Kanai S, Hirano M, Yokota A, Tanaka S, Miyasaka H. The rbcX gene product promotes the production and assembly of ribulose-1,5-bisphosphate carboxylase/oxygenase of Synechococcus sp. PCC7002 in Escherichia coli. Plant Cell Physiol. 2004 Oct;45(10):1390-5. doi: 10.1093/pcp/pch160. PMID:15564522 doi:http://dx.doi.org/10.1093/pcp/pch160
↑ Li Q, Jiang YL, Xia LY, Chen Y, Zhou CZ. Structural insights into cyanobacterial RuBisCO assembly coordinated by two chaperones Raf1 and RbcX. Cell Discov. 2022 Sep 20;8(1):93. PMID:36123352 doi:10.1038/s41421-022-00436-9