Abstract
Chloroplast proteins can be degraded in the intact organelle, but the relative rates of degradation vary considerably. To investigate regulatory aspects of glutamine synthetase (GS) degradation, isolated pea ( Pisum sativum L.) chloroplasts were used as a suitable system. Since chloroplasts were re-isolated after incubation, only chloroplasts remaining intact throughout the incubation and processes occurring therein were analysed. Net changes of nuclear-encoded proteins indicate degradation because protein synthesis is no longer possible under these conditions. Incubation of intact chloroplasts in a medium which promotes CO2 -assimilation led to the stabilisation of GS and several other chloroplast proteins. This general effect suggests that photosynthetic metabolism is relevant for the stability of stromal proteins. In addition, GS was specifically stabilised by methionine sulfoximine (MSO), a potent inhibitor of GS. However, other enzymes tested were not affected by MSO. When chloroplasts were incubated with methyl viologen, the degradation of several stromal enzymes including GS was accelerated, most likely by active oxygen species. Again, MSO specifically delayed the degradation of GS. As MSO is a substrate analogue, it appears likely that substrates or other ligands influence the susceptibility of enzymes against degradation systems present in the same compartment.
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Claims 8
Claim · model-written summary
A CO2 assimilation medium stabilized glutamine synthetase and other chloroplast proteins.
- Taxon
- pea
Lathyrus oleraceuse1 - Treatment
- a medium which promotes CO2 -assimilatione0
- Outcome
- stabilisation of GS and several other chloroplast proteinse0
- Direction
- stabilisatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Incubation of intact chloroplasts in a medium which promotes CO2 -assimilation led to the stabilisation of GS and several other chloroplast proteins.”
e1“isolated pea ( Pisum sativum L.) chloroplasts”
Claim · model-written summary
Methionine sulfoximine specifically stabilized glutamine synthetase.
- Taxon
- peaLathyrus oleraceuse1
- Treatment
- methionine sulfoximine (MSO)e0
- Gene
- GSe0
- Outcome
- GSe0
- Direction
- stabilisede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“GS was specifically stabilised by methionine sulfoximine (MSO)”
e1“isolated pea ( Pisum sativum L.) chloroplasts”
Claim · model-written summary
Methionine sulfoximine did not affect other tested enzymes.
- Taxon
- peaLathyrus oleraceuse1
- Treatment
- MSOe0
- Outcome
- other enzymese0
- Direction
- not affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“other enzymes tested were not affected by MSO”
e1“isolated pea ( Pisum sativum L.) chloroplasts”
Claim · model-written summary
Methyl viologen accelerated degradation of several stromal enzymes including glutamine synthetase.
- Taxon
- peaLathyrus oleraceuse1
- Treatment
- methyl viologene0
- Outcome
- degradation of several stromal enzymes including GSe0
- Direction
- acceleratede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When chloroplasts were incubated with methyl viologen, the degradation of several stromal enzymes including GS was accelerated”
e1“isolated pea ( Pisum sativum L.) chloroplasts”
Claim · model-written summary
Methionine sulfoximine delayed glutamine synthetase degradation under methyl viologen treatment.
- Taxon
- peaLathyrus oleraceuse1
- Treatment
- MSOe0
- Outcome
- degradation of GSe0
- Direction
- delayede0
- Qualifier
- methyl viologene0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When chloroplasts were incubated with methyl viologen, the degradation of several stromal enzymes including GS was accelerated, most likely by active oxygen species. Again, MSO specifically delayed the degradation of GS.”
e1“isolated pea ( Pisum sativum L.) chloroplasts”
Claim · model-written summary
Photosynthetic metabolism was proposed to support stromal protein stability.
- Taxon
- peaLathyrus oleraceuse1
- Outcome
- stability of stromal proteinse0
- Qualifier
- photosynthetic metabolisme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This general effect suggests that photosynthetic metabolism is relevant for the stability of stromal proteins.”
e1“isolated pea ( Pisum sativum L.) chloroplasts”
Claim · model-written summary
Active oxygen species were proposed to accelerate stromal enzyme degradation.
- Taxon
- peaLathyrus oleraceuse1
- Outcome
- degradation of several stromal enzymes including GSe0
- Qualifier
- active oxygen speciese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the degradation of several stromal enzymes including GS was accelerated, most likely by active oxygen species”
e1“isolated pea ( Pisum sativum L.) chloroplasts”
Claim · model-written summary
Substrates or ligands were proposed to influence enzyme susceptibility to degradation.
- Taxon
- peaLathyrus oleraceuse1
- Outcome
- susceptibility of enzymes against degradation systemse0
- Qualifier
- substrates or other ligandse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it appears likely that substrates or other ligands influence the susceptibility of enzymes against degradation systems present in the same compartment”
e1“isolated pea ( Pisum sativum L.) chloroplasts”
The same questions in other papers
methionine sulfoximine · molecular: metabolites · Lathyrus oleraceus (pea)Positive and negative results
1 in the opposite direction
- negative
co2 · molecular: metabolites · Lathyrus oleraceus (pea)Positive and negative results
2 papers in the same direction as this paper · 3 in the opposite direction
- negative
- no effect
- negative
2 papers more in this group
See all 6 papers →in vitro · molecular: metabolites · Lathyrus oleraceus (pea)Positive and negative results
2 papers in the same direction as this paper · 7 in the opposite direction
- no effect
- negative
- no effect
6 papers more in this group
See all 10 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.