Identification and characterization of multiple rubisco activases in chemoautotrophic bacteria

• Published in: Nature communications 2015-11, Vol.6 (1), p.8883-8883, Article 8883
• Main Authors: Tsai, Yi-Chin Candace, Lapina, Maria Claribel, Bhushan, Shashi, Mueller-Cajar, Oliver
• Format: Article
• Language: English
• Subjects: 101/28; 631/326/1320; 631/449/1734/1790; 631/45/173; 82; 82/16; 82/29; 82/80; 82/83; Acidithiobacillus - enzymology; Acidithiobacillus - genetics; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Carrier Proteins - genetics; Carrier Proteins - metabolism; Chemoautotrophic Growth; Enzyme Assays; Escherichia coli; Humanities and Social Sciences; Microscopy, Electron; multidisciplinary; Photosynthesis - genetics; Rhodobacter sphaeroides; Rhodopseudomonas; Rhodospirillum rubrum; Ribulose-Bisphosphate Carboxylase - metabolism; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms9883

Ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) is responsible for almost all biological CO 2 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. The CO 2 -fixing enzyme rubisco requires motor proteins known as rubisco activases to remove inhibitors bound to its active site. Here the authors describe a new class of rubisco activase present in chemoautotrophic bacteria that belongs to the MoxR family of AAA+ ATPases.