the effects of drought stress and exogenous abscisic acid on the expression of ribulose-1, 5-bisphosphate carboxyiase/oxygenase activase (rubisco activase) were examined in wheat (triticum aestivuml.). in response to water stress and abscisic acid, both the levels of endogenous abscisic acid and rubiscoactivase increased in the leaves. immunoblot analysis showed that both drought stress and abs...

The activation of purified ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) has been studied in the presence of sugar phosphates, and the effect of rubisco activase on this process determined. During an 11-minute time course at pH 7.7 and 11 micromolar CO(2), the activation of rubisco was strongly inhibited by ribulose-1,5-bisphosphate (4 millimolar), fructose-1,6-bisphosphate (1 milli...

Ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) activase protein was purified from spinach leaves by ammonium sulfate precipitation and ion exchange fast protein liquid chromatography. This resulted in 48-fold purification with 70% recovery of activity and yielded up to 18 milligrams of rubisco activase protein from 100 grams of leaves. Based on these figures, the protein comprised ap...

Ribulosebisphosphate carboxylase/oxygenase activase is a recently discovered enzyme that catalyzes the activation of ribulose-1,5-bisphosphate carboxylase/oxygenase ["rubisco"; ribulose-bisphosphate carboxylase; 3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39] in vivo. Clones of rubisco activase cDNA were isolated immunologically from spinach (Spinacea oleracea L.) and Arabidopsis...

Ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) is responsible for almost all biological CO2 assimilation, but forms inhibited complexes with its substrate ribulose-1,5-bisphosphate (RuBP) and other sugar phosphates. The distantly related AAA+ proteins rubisco activase and CbbX remodel inhibited rubisco complexes to effect inhibitor release in plants and α-proteobacteria, respectively...

The rate of CO(2) fixation by ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) following addition of ribulose 1,5-bisphosphate (RuBP) to fully activated enzyme, declined with first-order kinetics, resulting in 50% loss of rubisco activity after 10 to 12 minutes. This in vitro decline in rubisco activity, termed fall-over, was prevented if purified rubisco activase protein and ATP were ...

Abstract C4 plants, such as maize, strictly compartmentalize Rubisco to bundle sheath chloroplasts. The molecular basis for the restriction of from more abundant mesophyll chloroplasts is not fully understood. Mesophyll transcribe large subunit gene and, when normally quiescent transcription nuclear small family overcome by ectopic expression, still do accumulate measurable Rubisco. Here we sho...

In photosynthesis Rubisco catalyses the assimilation of CO(2) by the carboxylation of ribulose-1,5-bisphosphate. However, the catalytic properties of Rubisco are not optimal for current or projected environments and limit the efficiency of photosynthesis. Rubisco activity is highly regulated in response to short-term fluctuations in the environment, although such regulation may not be optimally...

The two isoforms of ribulose 1,2-bisphosphate carboxylase activase (Rbu-P2 carboxylase) from spinach (Spinacea oleracea L.) were individually purified from Escherichia coli transformed with expression vectors for the appropriate cDNAs. Both isoforms catalyzed activation of Rbu-P2 carboxylase (ribulose 1,5-bisphosphate carboxylase/oxygenase, EC 4.1.1.39) and ATP hydrolysis. The kinetics of the t...