6L1Q image
Entry Detail
PDB ID:
6L1Q
Keywords:
Title:
Crystal structure of AfCbbQ2, a MoxR AAA+-ATPase and CbbQO-type Rubisco activase from Acidithiobacillus ferrooxidans
Biological Source:
PDB Version:
Deposition Date:
2019-09-30
Release Date:
2019-12-18
Method Details:
Experimental Method:
Resolution:
2.20 Å
R-Value Free:
0.23
R-Value Work:
0.19
R-Value Observed:
0.19
Space Group:
P 6
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:CbbQ protein
Chain IDs:A (auth: C), B (auth: A), C (auth: B)
Chain Length:380
Number of Molecules:3
Biological Source:Acidithiobacillus ferrooxidans ATCC 23270
Primary Citation
Insights into the mechanism and regulation of the CbbQO-type Rubisco activase, a MoxR AAA+ ATPase.
Proc.Natl.Acad.Sci.USA 117 381 387 (2020)
PMID: 31848241 DOI: 10.1073/pnas.1911123117

Abstact

The vast majority of biological carbon dioxide fixation relies on the function of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco). In most cases the enzyme exhibits a tendency to become inhibited by its substrate RuBP and other sugar phosphates. The inhibition is counteracted by diverse molecular chaperones known as Rubisco activases (Rcas). In some chemoautotrophic bacteria, the CbbQO-type Rca Q2O2 repairs inhibited active sites of hexameric form II Rubisco. The 2.2-Å crystal structure of the MoxR AAA+ protein CbbQ2 from Acidithiobacillus ferrooxidans reveals the helix 2 insert (H2I) that is critical for Rca function and forms the axial pore of the CbbQ hexamer. Negative-stain electron microscopy shows that the essential CbbO adaptor protein binds to the conserved, concave side of the CbbQ2 hexamer. Site-directed mutagenesis supports a model in which adenosine 5'-triphosphate (ATP)-powered movements of the H2I are transmitted to CbbO via the concave residue L85. The basal ATPase activity of Q2O2 Rca is repressed but strongly stimulated by inhibited Rubisco. The characterization of multiple variants where this repression is released indicates that binding of inhibited Rubisco to the C-terminal CbbO VWA domain initiates a signal toward the CbbQ active site that is propagated via elements that include the CbbQ α4-β4 loop, pore loop 1, and the presensor 1-β hairpin (PS1-βH). Detailed mechanistic insights into the enzyme repair chaperones of the highly diverse CO2 fixation machinery of Proteobacteria will facilitate their successful implementation in synthetic biology ventures.

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