psbN

UniProt ID: A4GYT9
Organism: Populus trichocarpa
Review Status: DRAFT
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Gene Description

Chloroplast thylakoid membrane protein PsbN, a putative photosystem I/II biogenesis factor that is probably not a stable PSII core subunit.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0009535 chloroplast thylakoid membrane
IEA
GO_REF:0000120 		ACCEPT
Summary: Chloroplast thylakoid membrane is the correct localization for psbN.
Reason: UniProt places PsbN in the chloroplast thylakoid membrane.
Supporting Evidence:
file:POPTR/psbN/psbN-uniprot.txt
SUBCELLULAR LOCATION: Plastid, chloroplast thylakoid membrane
GO:0015979 photosynthesis
IEA
GO_REF:0000002 		KEEP AS NON CORE
Summary: Photosynthesis is broad pathway context for a putative photosystem biogenesis factor.
Reason: UniProt says PsbN may play a role in photosystem I and II biogenesis, but also cautions that it is probably not a PSII component.
Supporting Evidence:
file:POPTR/psbN/psbN-uniprot.txt
May play a role in photosystem I and II biogenesis.
file:POPTR/psbN/psbN-uniprot.txt
Originally thought to be a component of PSII; based on experiments in Synechocystis, N.tabacum and barley, and its absence from PSII in T.elongatus and T.vulcanus, this is probably not true.
GO:0016020 membrane
IEA
GO_REF:0000002 		MODIFY
Summary: Membrane is correct but too broad for PsbN.
Reason: Use the specific chloroplast thylakoid membrane localization supported by UniProt.
Proposed replacements: chloroplast thylakoid membrane
Supporting Evidence:
file:POPTR/psbN/psbN-uniprot.txt
SUBCELLULAR LOCATION: Plastid, chloroplast thylakoid membrane

Core Functions

Acts as a chloroplast thylakoid membrane protein with a probable role in photosystem biogenesis rather than as a stable photosystem II core subunit.

Cellular Locations:
chloroplast thylakoid membrane
Supporting Evidence:
  • file:POPTR/psbN/psbN-uniprot.txt
    May play a role in photosystem I and II biogenesis.
  • file:POPTR/psbN/psbN-uniprot.txt
    SUBCELLULAR LOCATION: Plastid, chloroplast thylakoid membrane
  • file:POPTR/psbN/psbN-uniprot.txt
    Originally thought to be a component of PSII; based on experiments in Synechocystis, N.tabacum and barley, and its absence from PSII in T.elongatus and T.vulcanus, this is probably not true.

References

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Suggested Questions for Experts

Q: Should Populus PsbN be annotated to a specific photosystem biogenesis or assembly process, and is the evidence strong enough despite the UniProt caution that it is probably not a PSII component?

Suggested Experiments

Experiment: Test PSI/PSII assembly and accumulation by blue-native PAGE and chlorophyll fluorescence in psbN perturbation or plastid-editing lines.

Type: targeted functional assay

📚 Additional Documentation

Notes

(psbN-notes.md)

psbN notes

  • UniProt identifies psbN as Protein PsbN [file:POPTR/psbN/psbN-uniprot.txt "RecName: Full=Protein PsbN"].
  • UniProt states PsbN may play a role in photosystem I and II biogenesis and places it in the chloroplast thylakoid membrane [file:POPTR/psbN/psbN-uniprot.txt "May play a role in photosystem I and II biogenesis"; file:POPTR/psbN/psbN-uniprot.txt "SUBCELLULAR LOCATION: Plastid, chloroplast thylakoid membrane"].
  • Because UniProt explicitly cautions that PsbN is probably not a PSII component, the review avoids adding PSII membership and treats broad photosynthesis as non-core pathway context.

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