Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the first committed step of carbon fixation in photosynthesis, but its efficiency is limited by slow turnover, due to the non-specific O2/CO2 binding and the blockade of sugar phosphates. To sustain catalytic activity, plants employ Rubisco activase (Rca), a chaperone ATPase that harnesses ATP hydrolysis to remodel Rubisco active site by engaging the N-terminal Rubisco large subunit (RbcL) and promoting the release of inhibitors. Despite its central role, the mechanistic basis of the Rubisco-Rca interaction remains unresolved due to the complex’s dynamic and heterogeneous nature. We are pursuing single-particle cryogenic electron microscopy (cryo-EM) to capture the Rubisco-Rca complex from higher plants, specifically Spinacia oleracea . Ongoing work focuses on optimizing protein purification, complex assembly, and EM sample preparation to stabilize and visualize this transient interaction. Preliminary data suggest that Rca assembles into higher order oligomers and interacts with Rubisco in a transient, dynamic manner. These efforts aim to obtain the first high-resolution and full-length structure of plant Rubisco engaged with Rca, providing mechanistic insight into how Rca restores Rubisco function to maintain carbon fixation. The outcome has broad implications for understanding photosynthetic regulation and guiding strategies to engineer crops with improved photosynthetic efficiency.
DeVore et al. (Sun,) studied this question.