A molecular dissection of the Rubisco activation system from rice
Date of Issue2017
School of Biological Sciences
Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) forms inhibited complexes with its own substrate RuBP and other sugar phosphates. The AAA+ protein Rubisco activase (Rca) counteracts this issue by removing these inhibitors and thus maintaining Rubisco in its functional state. Inactivation of Rca at moderately high temperatures is associated with the loss of the activation state of Rubisco. Here we present a detailed characterization of the Rubisco activase from rice (Oryza sativa). We then compare its properties to a highly functional and thermostable Rca system from the desert plant, Agave tequilana. An extensive mutational study identified a number of residues that are likely involved in the Rubisco-Rca interaction. Finally we present a modified model for Rubisco activation in plants. Our results indicate that bioprospecting and careful biochemical characterization of Rca homologues will lead to both mechanistic insights and identification of candidate proteins for engineering enhanced thermotolerance in rice.