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Title: The CbbQO-type rubisco activases encoded in carboxysome gene clusters can activate carboxysomal form IA rubiscos
Authors: Tsai, Candace Yi-Chin
Liew, Lynette
Guo, Zhijun
Liu, Di
Mueller-Cajar, Oliver
Keywords: Science::Biological sciences
Issue Date: 2022
Source: Tsai, C. Y., Liew, L., Guo, Z., Liu, D. & Mueller-Cajar, O. (2022). The CbbQO-type rubisco activases encoded in carboxysome gene clusters can activate carboxysomal form IA rubiscos. Journal of Biological Chemistry, 298(1), 101476-.
Project: MOE2016- T2-2-088
Journal: Journal of Biological Chemistry
Abstract: The CO2-fixing enzyme rubisco is responsible for almost all carbon fixation. This process frequently requires rubisco activase (Rca) machinery, which couples ATP hydrolysis to the removal of inhibitory sugar phosphates, including the rubisco substrate ribulose 1,5-bisphosphate (RuBP). Rubisco is sometimes compartmentalized in carboxysomes, bacterial microcompartments that enable a carbon dioxide concentrating mechanism (CCM). Characterized carboxysomal rubiscos, however, are not prone to inhibition, and often no activase machinery is associated with these enzymes. Here, we characterize two carboxysomal rubiscos of the form IAC clade that are associated with CbbQO-type Rcas. These enzymes release RuBP at a much lower rate than the canonical carboxysomal rubisco from Synechococcus PCC6301. We found that CbbQO-type Rcas encoded in carboxysome gene clusters can remove RuBP and the tight-binding transition state analog carboxy-arabinitol 1,5-bisphosphate from cognate rubiscos. The Acidithiobacillus ferrooxidans genome encodes two form IA rubiscos associated with two sets of cbbQ and cbbO genes. We show that the two CbbQO activase systems display specificity for the rubisco enzyme encoded in the same gene cluster, and this property can be switched by substituting the C-terminal three residues of the large subunit. Our findings indicate that the kinetic and inhibitory properties of proteobacterial form IA rubiscos are diverse and predict that Rcas may be necessary for some α-carboxysomal CCMs. These findings will have implications for efforts aiming to introduce biophysical CCMs into plants and other hosts for improvement of carbon fixation of crops.
ISSN: 0021-9258
DOI: 10.1016/j.jbc.2021.101476
Schools: School of Biological Sciences 
Rights: © 2021 The Authors. Published by Elsevier Inc on behalf of American Society for Biochemistry and Molecular Biology. This is an open access article under the CC BY license (
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:SBS Journal Articles

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