Biochemistry and Physiology of Leaf Proteins

Huffaker, R. C.

doi:10.1007/978-3-642-68237-7_11

Cited by 37 publications

(23 citation statements)

References 100 publications

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“…The Cys mutants were instrumental in this respect for examination of RuBisCO stability and degradation under stress con- ditions. Severe nitrogen starvation results in a decrease in RuBisCO content and activity (15,17), as was shown for wildtype cells, as well as the C247A and C192A mutants. However, RuBisCO mutated at Cys172 (C172A and C172A-C192A mutants) was hardly affected by the stress (Fig.…”

Section: Discussionsupporting

confidence: 60%

“…A sequence comparison of more than 500 RuBisCO genes revealed high levels of similarity, particularly among large subunits, and residues that form the catalytic site are entirely conserved (21). As a result of the enzymatic inefficiency manifested by a low catalytic turnover number (1.5 to 12 carboxylations s Ϫ1 catalytic site Ϫ1 [5,24]), as well as a low affinity for substrate CO 2 and competition between the CO 2 and O 2 substrates, it is accepted that the activity of RuBisCO limits both photosynthesis and photorespiration under various ecophysiological conditions (40).Due to the pivotal role of RuBisCO in photosynthesis, the activity, synthesis, and degradation of this enzyme are regulated by several mechanisms (4,17,32,40 …”

mentioning

confidence: 99%

“…Due to the pivotal role of RuBisCO in photosynthesis, the activity, synthesis, and degradation of this enzyme are regulated by several mechanisms (4,17,32,40…”

mentioning

confidence: 99%

“…Due to the pivotal role of RuBisCO in photosynthesis, the activity, synthesis, and degradation of this enzyme are regulated by several mechanisms (4,17,32,40); one of the less familiar of these mechanisms is redox potential regulation. Early work (26,39) demonstrated that thiol alkylating agents, such as p-mercury benzoate and iodoacetate, as well as HgCl 2 , inhibited the catalytic activity of the enzyme and increased the rate of enzyme proteolysis (36).…”

mentioning

confidence: 99%

“…Because of its high cellular concentration (10), RuBisCO not only is a catalyst but also is a storage protein for fixed nitrogen, sulfur, and carbon skeletons. These compounds may be reutilized under nutritional deficiency, aging, and stress conditions (12,15,17). GarciaFerris and Moreno (14) extended this hypothesis and suggested that free radicals produced under stress conditions and during nutritional limitation and maturation oxidize sulfhydryl groups on the enzyme and thus trigger enzyme degradation.…”

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confidence: 99%

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Dual Role of Cysteine 172 in Redox Regulation of Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase Activity and Degradation

et al. 2003

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Alkylation and oxidation of cysteine residues significantly decrease the catalytic activity and stimulate the degradation of ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO). We analyzed the role of vicinal cysteine residues in redox regulation of RuBisCO from Synechocystis sp. strain PCC 6803. Cys172 and Cys192, which are adjacent to the catalytic site, and Cys247, which cross-links two large subunits, were replaced by alanine. Whereas all mutant cells (C172A, C192A, C172A-C192A, and C247A) and the wild type grew photoautotrophically at similar rates, the maximal photosynthesis rates of C172A mutants decreased 10 to 20% as a result of 40 to 60% declines in RuBisCO turnover number. Replacement of Cys172, but not replacement of Cys192, prominently decreased the effect of cysteine alkylation or oxidation on RuBisCO. Oxidants that react with vicinal thiols had a less inhibitory effect on the activity of either the C172A or C192A enzyme variants, suggesting that a disulfide bond was formed upon oxidation. Thiol oxidation induced RuBisCO dissociation into subunits. This effect was either reduced in the C172A and C192A mutant enzymes or eliminated by carboxypentitol bisphosphate (CPBP) binding to the activated enzyme form. The CPBP effect presumably resulted from a conformational change in the carbamylated CPBP-bound enzyme, as implied from an alteration in the electrophoretic mobility. Stress conditions, provoked by nitrate deprivation, decreased the RuBisCO contents and activities in the wild type and in the C192A and C247A mutants but not in the C172A and C172A-C192A mutants. These results suggest that although Cys172 does not participate in catalysis, it plays a role in redox regulation of RuBisCO activity and degradation.The universal CO 2 -fixing enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) (EC 4.1.1.39) catalyzes the primary reactions of photosynthesis and photorespiration by carboxylation and oxygenation of ribulose-1,5-bisphosphate (RuBP), respectively. The RuBisCO from cyanobacteria, algae (excluding some dinoflagellates), and higher plants is a hexadecamer consisting of eight large and eight small subunits organized as four protomers, each of which has two active sites at the interface between each large subunit pair (3,4,29). In the RuBisCO of many species, an intradimeric disulfide bond is formed under oxidizing conditions between the Cys247 residues of a large subunit pair (30). A sequence comparison of more than 500 RuBisCO genes revealed high levels of similarity, particularly among large subunits, and residues that form the catalytic site are entirely conserved (21). As a result of the enzymatic inefficiency manifested by a low catalytic turnover number (1.5 to 12 carboxylations s Ϫ1 catalytic site Ϫ1 [5,24]), as well as a low affinity for substrate CO 2 and competition between the CO 2 and O 2 substrates, it is accepted that the activity of RuBisCO limits both photosynthesis and photorespiration under various ecophysiological conditions (40).Due to the pivotal role of RuB...

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Section: Discussionsupporting

confidence: 60%

mentioning

confidence: 99%

“…Due to the pivotal role of RuBisCO in photosynthesis, the activity, synthesis, and degradation of this enzyme are regulated by several mechanisms (4,17,32,40…”

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Dual Role of Cysteine 172 in Redox Regulation of Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase Activity and Degradation

et al. 2003

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Chloroplast-Retention in Ciliated Protozoa

Stoecker

1992

Origins of Plastids

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Oxidative modification and breakdown of ribulose-1,5-bisphosphate carboxylase/oxygenase induced in Euglena gracitis by nitrogen starvation

García-Ferris

Moreno

1994

Planta

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When photoheterotrophic Euglena gracilis Z Pringsheim was subjected to nitrogen (N)-deprivation, the abundant photosynthetic enzyme ribulose-l,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) was rapidly and selectively degraded. The breakdown began after a 4-h lag period and continued for a further 8 h at a steady rate. After 12 h of starvation, when the amount of Rubisco was reduced to 40%, the proteolysis of this enzyme slowed down while degradation of other proteins started at a similar pace. This resulted in a decline of culture growth, chloroplast disassembly as witnessed by chlorophyll (Chl) loss -and cell bleaching. Experiments with spectinomycin, an inhibitor of chloroplastic translation, indicated that there was an absolute increase in the rate of Rubisco degradation in the N-deprived culture as compared with control conditions, where no significant carboxylase breakdown was detected. Oxidative aggregation of Rubisco (as detected by non-reductive electrophoresis) and association of the enzyme to membranes increased with time of N-starvation. Fluorescent labeling of oxidized cysteine (Cys) residues with monobromobimane indicated a progressive oxidation of Cys throughout the first hours of N-deprivation. It is concluded that Rubisco acts as an N store in Euglena, being first oxidized, and then degraded, during Nstarvation. The mobilization of Rubisco allows sustained cell growth and division, at almost the same rate as the control (non-starved) culture, during 12 h of N-deprivation. Afterwards, breakdown is extended to other photosynthetic structures and the whole chloroplast is dismantled while cell growth is greatly reduced.

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Biochemistry and Physiology of Leaf Proteins

Cited by 37 publications

References 100 publications

Dual Role of Cysteine 172 in Redox Regulation of Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase Activity and Degradation

Dual Role of Cysteine 172 in Redox Regulation of Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase Activity and Degradation

Chloroplast-Retention in Ciliated Protozoa

Oxidative modification and breakdown of ribulose-1,5-bisphosphate carboxylase/oxygenase induced in Euglena gracitis by nitrogen starvation

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