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Title: Insights into the mechanism and regulation of the CbbQO-type Rubisco activase, a MoxR AAA+ ATPase
Authors: Tsai, Candace Yi-Chin
Ye, Fuzhou
Liew, Lynette
Liu, Di
Bhushan, Shashi
Gao, Yong-Gui
Mueller-Cajar, Oliver
Keywords: Science::Biological sciences
Issue Date: 2020
Source: Tsai, C. Y., Ye, F., Liew, L., Liu, D., Bhushan, S., Gao, Y. & Mueller-Cajar, O. (2020). Insights into the mechanism and regulation of the CbbQO-type Rubisco activase, a MoxR AAA+ ATPase. Proceedings of the National Academy of Sciences of the United States of America, 117(1), 381-387.
Project: MOE2016-T2-2-088
Journal: Proceedings of the National Academy of Sciences of the United States of America
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 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.
ISSN: 0027-8424
DOI: 10.1073/pnas.1911123117
DOI (Related Dataset): 10.21979/N9/K4IROM
Rights: © 2020 The Author(s) (Published under the PNAS license). All rights reserved.
Fulltext Permission: none
Fulltext Availability: No Fulltext
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