Identification and characterization of multiple rubisco activases in chemoautotrophic bacteria

• Main Authors: Tsai, Yi-Chin Candace, Lapina, Maria Claribel, Bhushan, Shashi, Mueller-Cajar, Oliver
• Other Authors: School of Biological Sciences
• Format: Article
• Language: English
• Published: 2017
• Subjects: Enzyme Mechanisms; Bacteriology
• Online Access: https://hdl.handle.net/10356/83887; http://hdl.handle.net/10220/42865
• Institution: Nanyang Technological University

Ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) is responsible for almost all biological CO2 assimilation, but forms inhibited complexes with its substrate ribulose-1,5-bisphosphate (RuBP) and other sugar phosphates. The distantly related AAA+ proteins rubisco activase and CbbX remodel inhibited rubisco complexes to effect inhibitor release in plants and α-proteobacteria, respectively. Here we characterize a third class of rubisco activase in the chemolithoautotroph Acidithiobacillus ferrooxidans. Two sets of isoforms of CbbQ and CbbO form hetero-oligomers that function as specific activases for two structurally diverse rubisco forms. Mutational analysis supports a model wherein the AAA+ protein CbbQ functions as motor and CbbO is a substrate adaptor that binds rubisco via a von Willebrand factor A domain. Understanding the mechanisms employed by nature to overcome rubisco’s shortcomings will increase our toolbox for engineering photosynthetic carbon dioxide fixation.