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Identification and characterization of multiple rubisco activases in chemoautotrophic bacteria.

Tsai YC, Lapina MC, Bhushan S, Mueller-Cajar O - Nat Commun (2015)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551. Singapore.

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.

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Related in: MedlinePlus

Inhibited rubisco complexes stimulate CbbQO ATPase activity.(a,b) ATPase activity assays of Q1O1 (a) and Q2O2 (b) (0.27 μM oligomer) in the presence of varying concentrations of inhibited AfLS (a) or AfM (b) complexes. (c) The ATPase stimulation is isoform specific. ATPase activity of 0.27 μM QO complex was measured in the presence (coloured bars) and absence (black bars) of the indicated rubisco complex (3 μM active sites). Error bars indicate the mean and s.d. of at least three independent experiments.
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f4: Inhibited rubisco complexes stimulate CbbQO ATPase activity.(a,b) ATPase activity assays of Q1O1 (a) and Q2O2 (b) (0.27 μM oligomer) in the presence of varying concentrations of inhibited AfLS (a) or AfM (b) complexes. (c) The ATPase stimulation is isoform specific. ATPase activity of 0.27 μM QO complex was measured in the presence (coloured bars) and absence (black bars) of the indicated rubisco complex (3 μM active sites). Error bars indicate the mean and s.d. of at least three independent experiments.

Mentions: Both AfQ2 and Q2O2ΔC444 displayed a low ATPase activity of <1 min−1 protomer CbbQ−1 (Supplementary Fig. 9g). In contrast both Q1O1 and Q2O2 hydrolysed ATP with a specific activity of ∼3 min−1 protomer CbbQ−1. Therefore, the interaction of the full length CbbO subunit with the CbbQ hexamer induces a conformational change that increases the basal ATP hydrolysis rate of CbbQ. The ATPase activity of both QO systems (but not AfQ2 or Q2O2ΔC444) was specifically stimulated by their respective ER and ECMC complexes in a concentration-dependent manner, resembling the behaviour of CbbX19 (Fig. 4a,b, Supplementary Fig. 9g). In contrast, the ATPase activity of Rca is not stimulated by inhibited rubisco complexes51.


Identification and characterization of multiple rubisco activases in chemoautotrophic bacteria.

Tsai YC, Lapina MC, Bhushan S, Mueller-Cajar O - Nat Commun (2015)

Inhibited rubisco complexes stimulate CbbQO ATPase activity.(a,b) ATPase activity assays of Q1O1 (a) and Q2O2 (b) (0.27 μM oligomer) in the presence of varying concentrations of inhibited AfLS (a) or AfM (b) complexes. (c) The ATPase stimulation is isoform specific. ATPase activity of 0.27 μM QO complex was measured in the presence (coloured bars) and absence (black bars) of the indicated rubisco complex (3 μM active sites). Error bars indicate the mean and s.d. of at least three independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4660213&req=5

f4: Inhibited rubisco complexes stimulate CbbQO ATPase activity.(a,b) ATPase activity assays of Q1O1 (a) and Q2O2 (b) (0.27 μM oligomer) in the presence of varying concentrations of inhibited AfLS (a) or AfM (b) complexes. (c) The ATPase stimulation is isoform specific. ATPase activity of 0.27 μM QO complex was measured in the presence (coloured bars) and absence (black bars) of the indicated rubisco complex (3 μM active sites). Error bars indicate the mean and s.d. of at least three independent experiments.
Mentions: Both AfQ2 and Q2O2ΔC444 displayed a low ATPase activity of <1 min−1 protomer CbbQ−1 (Supplementary Fig. 9g). In contrast both Q1O1 and Q2O2 hydrolysed ATP with a specific activity of ∼3 min−1 protomer CbbQ−1. Therefore, the interaction of the full length CbbO subunit with the CbbQ hexamer induces a conformational change that increases the basal ATP hydrolysis rate of CbbQ. The ATPase activity of both QO systems (but not AfQ2 or Q2O2ΔC444) was specifically stimulated by their respective ER and ECMC complexes in a concentration-dependent manner, resembling the behaviour of CbbX19 (Fig. 4a,b, Supplementary Fig. 9g). In contrast, the ATPase activity of Rca is not stimulated by inhibited rubisco complexes51.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551. Singapore.

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.

Show MeSH
Related in: MedlinePlus