Purification and initial characterization of the CbbQ-CbbO protein complex from acidithiobacillus ferrooxidans, a possible rubisco activation system of chemoautotrophic bacteria.

• Main Author: Guo, ZhiJun.
• Other Authors: School of Biological Sciences
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Science::Biological sciences::Biochemistry
• Online Access: http://hdl.handle.net/10356/52946
• Institution: Nanyang Technological University

Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the fixation of CO2 via the Calvin Benson Bassham cycle. Rubisco is prone to inhibition by its substrate Ribulose 1,5-bisphosphate, which tightly binds to the uncarbamylated active site. In plants and red algae, an ATPase associated with various cellular activities protein rubisco activase (Rca and CbbX) can reactivate the inhibited rubisco complex in an ATP-dependent manner (Mueller-Cajar et al., 2013). However, there are no known rubisco activase in chemoautotrophic bacteria. Here we report the CbbQ-CbbO complex, as a potential rubisco activase of rubisco from chemoautotrophic bacteria .The recombinant AfCbbQ2O2 complex from Acidithiobacillus ferrooxidans was purified from Escherichia coli. ATPase activity was measured spectrophotometrically using a coupled enzymatic assay (Barta et al., 2011). AfCbbQ2O2 was stimulated by inhibited form II rubisco in a concentration dependent manner and had maximum activity of 65.7 min-1. This result was consistent with the behavior of the genuine activase CbbX and supports the role of AfCbbQ2O2 as a potential rubisco activase candidate. A novel rubisco activase system would provide insights into aspects of the rubisco activation mechanism that had not been characterized with existing rubisco activase. Increased understanding of rubisco activation mechanisms may contribute towards increasing photosynthetic performance of crops.