title: Identification and characterization of multiple rubisco activases in chemoautotrophic bacteria.
abstract: 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.
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551. Singapore.
authors.forename: Yi-Chin Candace
authors.initials: YC
authors.lastname: Tsai
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551. Singapore.
authors.forename: Maria Claribel
authors.initials: MC
authors.lastname: Lapina
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551. Singapore.
authors.forename: Shashi
authors.initials: S
authors.lastname: Bhushan
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551. Singapore.
authors.forename: Oliver
authors.initials: O
authors.lastname: Mueller-Cajar
mesh_terms: D042763:Acidithiobacillus / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D052837:Chemoautotrophic Growth; D057075:Enzyme Assays; D004926:Escherichia coli; D008854:Microscopy, Electron; D010788:Photosynthesis / Q000235:genetics; D012242:Rhodobacter sphaeroides; D012241:Rhodopseudomonas; D012247:Rhodospirillum rubrum; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; C092405:CbbQ protein, bacteria; D012273:Ribulose-Bisphosphate Carboxylase