Probing the rice Rubisco-Rubisco activase interaction via subunit heterooligomerization

• Main Authors: Shivhare, Devendra, Ng, Jediael, Tsai, Candace Yi-Chin, Mueller-Cajar, Oliver
• Other Authors: School of Biological Sciences
• Format: Article
• Language: English
• Published: 2021
• Subjects: Science::Biological sciences; Rubisco Activase; Photosynthesis
• Online Access: https://hdl.handle.net/10356/151574
• Institution: Nanyang Technological University

During photosynthesis the AAA+ protein and essential molecular chaperone Rubisco activase (Rca) constantly remodels inhibited active sites of the CO₂-fixing enzyme Rubisco (ribulose 1,5-bisphosphate carboxylase/oxygenase) to release tightly bound sugar phosphates. Higher plant Rca is a crop improvement target, but its mechanism remains poorly understood. Here we used structure-guided mutagenesis to probe the Rubisco-interacting surface of rice Rca. Mutations in Ser-23, Lys-148, and Arg-321 uncoupled adenosine triphosphatase and Rca activity, implicating them in the Rubisco interaction. Mutant doping experiments were used to evaluate a suite of known Rubisco-interacting residues for relative importance in the context of the functional hexamer. Hexamers containing some subunits that lack the Rubisco-interacting N-terminal domain displayed a ∼2-fold increase in Rca function. Overall Rubisco-interacting residues located toward the rim of the hexamer were found to be less critical to Rca function than those positioned toward the axial pore. Rca is a key regulator of the rate-limiting CO₂-fixing reactions of photosynthesis. A detailed functional understanding will assist the ongoing endeavors to enhance crop CO₂ assimilation rate, growth, and yield.