Protein: K(+) efflux antiporter 3, chloroplastic (AtKEA3) (Protein DISTURBED PROTON GRADIENT REGULATION) (Q9M0Z3)
Organism: Arabidopsis thaliana (Mouse-ear cress)
Function: Electroneutral K(+)/H(+) efflux antiporter assuring proton efflux from the thylakoid lumen to the plastid stroma, thus increasing the membrane potential at the expense of the proton gradient (delta pH) component of the proton motive force (PMF). Promotes photosynthesis and growth in conditions where the chloroplast (cp)ATP synthase activity is low (e.g. cgl160 mutant background) by reducing the pH gradient across the thylakoid membrane. Accelerates photosynthetic acclimation in fluctuating light environments by modulating two components of the proton motive force, the proton gradient and the electric potential (delta Psi). Promotes the relaxation of photoprotective energy-dependent non-photochemical quenching (NPQ) after transitions from high to low light, thus enhancing photosystem II (PSII) quantum efficiency in fluctuating light. On transition from high to low light, slows down photoprotection by dissipating the pH gradient across the thylakoid membrane. During photosynthetic response on transition from dark to low light, involved in a sequential mechanism of adaptation; VCCN1 and CLCe first trigger the activation of photoprotection, which is later down-regulated by KEA3 to a low steady state, while adjusting electron transport. Together with the chloroplast NADH dehydrogenase-like (NDH) complex, maximizes photosynthesis efficiency after a long dark adaptation. Required in roots for rapid hyperosmotic-induced Ca(2+) responses and for osmo-sensory potentiation in hyperosmotic conditions.
Subcellular location: Plastid, chloroplast membrane {ECO:0000269|PubMed:18431481}; Multi-pass membrane protein {ECO:0000255}. Golgi apparatus membrane {ECO:0000269|PubMed:24278440}; Multi-pass membrane protein {ECO:0000255}. Plastid, chloroplast thylakoid membrane {ECO:0000269|PubMed:24794527, ECO:0000269|PubMed:25451040, ECO:0000269|PubMed:27783435, ECO:0000269|PubMed:31053658, ECO:0000269|PubMed:32041909}; Multi-pass membrane protein {ECO:0000255}. Note=Enriched in the stromal lamellae. {ECO:0000269|PubMed:25451040}.
Interaction partners:
- Two-pore potassium channel 3
- Chloride channel protein CLC-e
- F-actin-capping protein subunit alpha
- PITH domain-containing protein At3g04780
- Cation/H
- Protein PROTON GRADIENT REGULATION 5
- Cation/H
- Sodium/proton antiporter 1
- Sodium/hydrogen exchanger 5
- Photosystem II 22 kDa protein, chloroplastic
Sequence:
MAISTMLGSISCCPSPKGYEMVKQHSVRLKHCVFTVKSSVPVYSEGVNDGIKLHSFGNLVKKKVFLDTSKRFYFQGRWSESSGRRVETYAGVDVASAVDVINDLGFDTLTFLMVTVIIVPAFRILKASPILGFFFAGVVLNQFGLIRNLTDVKVLSEWGILFLLFEMGLELSLARLKALAKFAFGMGLTQVLLCTAAFTAFELPPNGAIGTKILEFLFHSRPDLVNIRSIDEAVVIGAALSLSSSAFVLQLLAEKGELPTRFGSATLGILLLQDIAVVPLLVILPVLESQDIGGESIWPMLAKESAKALGGLGILSLGGKFFLRRIFEVVAETRSSEAFVALCLLTVAGTSLVTQWLGFSDTLGAFLAGALLAETNFRTQIEADIRPFRGLLLGLFFVTTGTSIDMEVLFREWPNVLSLLGGLIVIKTLIITAIGPRVGLTIQESVRVGFLLSQGGEFAFVVFSLANRLGVLPNELNKLLIIVVVLSMALTPYLNQLGRKAADFLDERLDPGEKIGEDVNFDVSESIVIIGFGQMGQVLANFLSTPLVSDSDLVGWPYIGFDLNPAVVKESRKLGFPILYGDGSRPSVLQSAGVSSPKAIMIMYKGKKRTTEAVQRLRLAFPGSPIYARAQDLPHLLELKKAGATDAILENAETSLQLGSKLLTGFGVMSDDVSFLSKVFRDSMEIQAQEEITASETNAGLKPMQMKASDINVVSAATQKQVQLMKPMQMKASDSNSDSAAEILQETAGLSQPPEIDDSSVNIDNGFVGKADKAQD