Cloning, Expression and Interaction Studies of the Potential RubisCO Activase CbbQ

Carboxysomes are polyhedral microcompartments found in all cyanobacteria and in many chemoautotrophs. Within their shell they contain the enzyme ribulose-1, 5-bisphosphate carboxylase/oxygenase (RubisCO), which fixes CO2. Downstream of the carboxysome operon there is another gene cluster containing several genes that may enhance carboxysome function. Two of these genes, cbbQ and cbbO, encode potential RubisCO activases. Using recombinant CbbQ and CbbO protein, and RubisCO isolated from carboxysomes the interaction between these proteins was studied. The CbbO and CbbQ proteins were both His tagged, allowing them to be purified with Ni2+-NTA column chromatography. Each of these tagged proteins was incubated with RubisCO on a Ni2+-NTA column to determine if both proteins could be co-eluted. These studies suggest that recombinant CbbO and CbbQ do not interact individually with RubisCO. Since His-tagged CbbO and untagged CbbQ, when co-expressed in E. coli, form a complex, ongoing studies are focused on determining if both potential activases are needed to interact with RubisCO when co-expressed. --Page iv.

Carboxysomes are polyhedral microcompartments found in all cyanobacteria and in many chemoautotrophs.