Protein: Light-harvesting complex stress-related protein 3.1, chloroplastic (Chlorophyll a-b binding protein LHCSR3.1) (P0DO19)
Organism: Chlamydomonas reinhardtii (Chlamydomonas smithii)
Function: Required for non-photochemical quenching (NPQ), a mechanism that converts and dissipates the harmful excess absorbed light energy into heat and protect the photosynthetic apparatus from photo-oxidative damage. NPQ includes dissipating excess light energy to heat (qE) and the reversible coupling of LHCII to photosystems (state transitions or qT), which are considered separate NPQ mechanisms. Is responsible for most of the excess light energy to heat dissipation (qE), also known as energy-dependent chlorophyll fluorescence quenching activity of chlorophyll excited states. Involved in a de-coupling and re-coupling of energy transfer to photosystem II (PSII) during qT. Binds chlorophyll a and b. Is able to sense luminal acidification of the thylakoid membranes, which occurs along with elevated electron flow caused by excess light. Establishes interactions with photosystem II (PSII) antenna components upon lumen acidification, and protonation of lumen-exposed, negatively charged residues both in LHCSR3 and in PSII antenna components. Mediates excitation energy transfer from light-harvesting complex II (LHCII) to photosystem I (PSI), rather than photosystem II (PSII), at low pH, which mimics the acidified lumen of the thylakoid membranes in high light-exposed chloroplasts. Activates PSI-dependent fluorescence quenching in addition to dissipating excitation energy in LHCII to avoid photooxidative stress under excess light. Contributes with PGRL1 to the regulation of electron flow upstream of photosystem I (PSI), and limits the accumulation of electrons on the PSI acceptor side, thus avoiding PSI photoinhibition.
Subcellular location: Plastid, chloroplast thylakoid membrane {ECO:0000305}; Multi-pass membrane protein {ECO:0000255}.
Sequence: MLANVVSRKASGLRQTPARATVAVKSVSGRRTTAAEPQTAAPVAAEDVFAYTKNLPGVTAPFEGVFDPAGFLATASIKDVRRWRESEITHGRVAMLAALGFVVGEQLQDFPLFFNWDGRVSGPAIYHFQQIGQGFWEPLLIAIGVAESYRVAVGWATPTGTGFNSLKDDYEPGDLGFDPLGLKPTDPEELKVMQTKELNNGRLAMIAIAAFVAQELVEQTEIFEHLALRFEKEAILELDDIERDLGLPVTPLPDNLKSL
InterPro domains: - IPR022796: Chlorophyll A-B binding protein (family) [53-216]
- IPR001344: Chlorophyll A-B binding protein, plant and chromista (family) [13-228]
Interaction partners: - Photosystem II protein PSBS1
- Photosystem II protein PSBS2
- Chlorophyll a-b binding protein
- Uncharacterized protein
- Phototropin
- Chlorophyll a-b binding protein
- Photosystem I P700 chlorophyll a apoprotein A1
Gene Ontology annotations:
Molecular Function (MF): GO:0003674 (molecular function), GO:0005488 (binding), GO:0005515 (protein binding), GO:0042802 (identical protein binding)
Biological Process (BP): GO:0008150 (biological process), GO:0050896 (response to stimulus), GO:0009628 (response to abiotic stimulus), GO:0006950 (response to stress), GO:0006979 (response to oxidative stress), GO:0009314 (response to radiation), GO:0009416 (response to light stimulus), GO:0009642 (response to light intensity), GO:0009644 (response to high light intensity)
Cellular Component (CC): GO:0005575 (cellular component), GO:0110165 (cellular anatomical entity), GO:0005622 (intracellular anatomical structure), GO:0043226 (organelle), GO:0016020 (membrane), GO:0043229 (intracellular organelle), GO:0034357 (photosynthetic membrane), GO:0043228 (non-membrane-bounded organelle), GO:0042651 (thylakoid membrane), GO:0043232 (intracellular non-membrane-bounded organelle), GO:0009579 (thylakoid)