Rubisco's chiropractor: a study of higher plant Rubisco activase
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Rubisco activase operates as the chaperone responsible for maintaining the catalytic competency of Ribulose 1,5-bisphophate carboxylase oxygenase (Rubisco) in plants. Rubisco is notoriously inefficient, rapidly self-inactivating under physiological conditions. Rubisco activase uses the power released from the hydrolysis of ATP to power a conformational change in Rubisco, reactivating it. Rubisco activase has been previously shown to form a large range of species in solution; however, little has been done to relate the size of oligomeric species and physiological activity. In this thesis data is presented from a range of biophysical techniques including analytical ultracentrifugation, static light scattering, and small angle X-ray scattering combined with activity assays to show a strong relationship between oligomeric state and activity. The results suggest that small oligomers comprising 2-4 subunits are sufficient to attain full specific activity, a highly unusual property for enzymes from the AAA+ family. Studies utilising a number of Rubisco activase variants enabled the determination of how Rubisco and Rubisco activase may interact within a plant cell. A detailed characterisation of the α-, β-, and a mixture of isoforms further broadened our knowledge on the oligomerisation of Rubisco activase. Of particular importance was the discovery of a thermally stable hexameric Rubisco activase variant. It is hoped that these findings may contribute to development of more heat tolerant Rubisco activase and lead research into more drought resilient crop plants.