6L1Q

Crystal structure of AfCbbQ2, a MoxR AAA+-ATPase and CbbQO-type Rubisco activase from Acidithiobacillus ferrooxidans

Summary for 6L1Q

• Entry DOI: 10.2210/pdb6l1q/pdb
• Descriptor: CbbQ protein, ADENOSINE-5'-DIPHOSPHATE, PHOSPHATE ION, ... (4 entities in total)
• Functional Keywords: aaa+ atpase, cbbqo-type rubisco activase, moxr family, molecular chaperone, chaperone
• Biological source: Acidithiobacillus ferrooxidans ATCC 23270
• Total number of polymer chains: 3
• Total formula weight: 127496.46

Authors

Ye, F.Z.,Tsai, Y.C.C.,Mueller-Cajar, O.,Gao, Y.G. (deposition date: 2019-09-30, release date: 2019-12-18, Last modification date: 2023-11-22)

Primary citation

Tsai, Y.C.,Ye, F.,Liew, L.,Liu, D.,Bhushan, S.,Gao, Y.G.,Mueller-Cajar, O.
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

PubMed Abstract: 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 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 CO fixation machinery of Proteobacteria will facilitate their successful implementation in synthetic biology ventures.

PubMed: 31848241
DOI: 10.1073/pnas.1911123117

Experimental method

X-RAY DIFFRACTION (2.2 Å)