Light Activation of Rubisco by Rubisco Activase and Thylakoid Membranes

摘要

A reconstituted system comprising ribulose bisphosphate carboxylase/oxygenase (rubisco), rubisco activase, washed thylakoid membranes, and ATP was used to demonstrate a light-dependent stimulation of rubisco activation. ATP, ribulose bisphosphate, H+, and Mg2+concentrations are normally light-dependent variables in the chloroplast but were maintained at pre-determined levels. Results indicated that rubisco activase and washed thylakoid membranes are sufficient to catalyze light stimulation of rubisco activation with the reconstituted system, and that rubisco activase is required for this light stimulation. The washed thylakoid membranes did not exhibit rubisco activase activity, nor was rubisco activase protein detected immunologically. Light-dependent activation of rubisco in the reconstituted system was similar in whole-chain and PS I electron transport reactions, and saturated at approximately 100μmol photons m−2s