Low-CO2-inducible protein 5, a chloroplast thylakoid-associated phosphoprotein that is strongly induced under carbon-limiting conditions as part of the carbon concentrating mechanism (CCM) in Chlamydomonas reinhardtii. While its precise molecular function remains unknown, LCI5 undergoes redox-dependent phosphorylation exclusively under low CO2 conditions and likely plays a regulatory or structural role in optimizing photosynthetic efficiency during carbon limitation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005515 protein binding | IEA | NEW | Summary: LCI5 likely binds to other CCM components as part of its regulatory or structural role in the carbon concentrating mechanism. Reason: This molecular function term reflects LCI5's likely role in protein-protein interactions within the carbon concentrating mechanism, though specific binding partners remain unknown. Supporting Evidence: file:CHLRE/LCI5/LCI5-deep-research.md LCI5 clusters with Rubisco and other CCM-related proteins in co-expression analysis, suggesting functional interactions |
| GO:0009535 chloroplast thylakoid membrane | IEA | NEW | Summary: LCI5 is localized to the stromal side of chloroplast thylakoid membranes where it undergoes redox-dependent phosphorylation. Reason: This cellular component term reflects LCI5's established subcellular localization to the thylakoid membrane where it functions as part of the carbon concentrating mechanism. Supporting Evidence: PMID:16572472 Lci5 was localized in chloroplast and confined to the stromal side of the thylakoid membranes |
| GO:0009570 chloroplast stroma | IEA | NEW | Summary: LCI5 is specifically localized to the stromal side of thylakoid membranes, which places it within the chloroplast stroma compartment. Reason: This cellular component term reflects LCI5's location on the stromal side of thylakoid membranes, technically positioning it within the chloroplast stroma where it can interact with CCM components. Supporting Evidence: PMID:16572472 Immunoblotting with Lci5-specific antibodies revealed that Lci5 was localized in chloroplast and confined to the stromal side of the thylakoid membranes. file:CHLRE/LCI5/LCI5-deep-research.md LCI5 clusters with Rubisco and other CCM-related proteins, which are located in the chloroplast stroma |
| GO:0015976 carbon utilization | IEA | NEW | Summary: LCI5 is part of the carbon concentrating mechanism (CCM) that optimizes carbon utilization under limiting CO2 conditions. Reason: This biological process term reflects LCI5's role in the carbon concentrating mechanism that enhances carbon utilization efficiency in Chlamydomonas under low CO2 conditions. Supporting Evidence: PMID:16572472 Phosphorylation of Lci5 and UEP occurred strictly at limiting CO2; it required reduction of electron carriers in the thylakoid membrane PMID:18322145 Although the function of LCI5 is unknown at present, posttranslational modification of proteins during the acclimation process to LC conditions, which cannot be identified by a DNA array analysis, could be associated with the CCM induction. file:CHLRE/LCI5/LCI5-deep-research.md LCI5 clusters with Rubisco and other CCM-related proteins that optimize carbon utilization |
| GO:0015979 photosynthesis | IEA | NEW | Summary: LCI5 contributes to photosynthetic efficiency by optimizing the carbon concentrating mechanism under limiting CO2 conditions. Reason: This biological process term reflects LCI5's role in optimizing photosynthetic carbon fixation through the carbon concentrating mechanism that enhances photosynthetic efficiency under low CO2. Supporting Evidence: PMID:16572472 Phosphorylation of Lci5 and UEP occurred strictly at limiting CO2; it required reduction of electron carriers file:CHLRE/LCI5/LCI5-deep-research.md LCI5 clusters with Rubisco and other CCM-related proteins that enhance photosynthetic carbon fixation PMID:33230314 Approximately one-third of global CO2 fixation occurs in a phase-separated algal organelle called the pyrenoid |
| GO:0071244 cellular response to carbon dioxide | IEA | NEW | Summary: LCI5 is strongly induced under carbon-limiting conditions and undergoes redox-dependent phosphorylation specifically in response to low CO2 availability. Reason: This biological process term captures LCI5's primary function as a low-CO2-inducible protein that responds to carbon dioxide availability through post-translational modification and expression changes. Supporting Evidence: PMID:16572472 Phosphorylation of Lci5 and UEP occurred strictly at limiting CO2; it required reduction of electron carriers in the thylakoid membrane, but was not induced by light. PMID:18322145 Although the function of LCI5 is unknown at present, posttranslational modification of proteins during the acclimation process to LC conditions, which cannot be identified by a DNA array analysis, could be associated with the CCM induction. |
| GO:0043169 cation binding | NAS | NEW | Summary: Added to align core_functions with existing annotations. Reason: Core function term not present in existing_annotations. |
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Download this section (compressed HTML)Q: How does LCI5 contribute to CO2 concentrating mechanisms in Chlamydomonas photosynthesis?
Q: What determines the subcellular localization of LCI5 and how does this affect its function?
Q: How is LCI5 expression regulated in response to CO2 availability and light conditions?
Q: What role does LCI5 play in algal adaptation to different environmental carbon conditions?
Experiment: Photosynthetic measurements in LCI5 mutant strains to assess CO2 concentrating mechanism function
Experiment: Subcellular localization studies using fluorescent protein fusions to determine LCI5 distribution
Experiment: RNA-seq analysis under different CO2 conditions to study LCI5 regulation and downstream targets
Experiment: Proteomics analysis of carbon concentrating mechanism components to understand LCI5 protein interactions
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