|Gene:||psaE2||Accession Number: G-668 (MetaCyc)|
Species: Arabidopsis thaliana col
Component of: photosystem I (extended summary available)
Hydrophilic stromal PSI-E stabilizes the interaction between psaC and the PSI core, assists in the docking of ferredoxin to PSI and interacts with ferredoxin-NADP oxidoreductase. PSI-E is required for optimal electron transport to ferredoxin and flavodoxin [Rousseau93].
It is encoded in the nucleus and has an extended N-terminal region. There are two isoforms of the protein.
Molecular Weight of Polypeptide: 15.18 kD (from nucleotide sequence)
|Cellular Component:||GO:0009507 - chloroplast|
Revised 06-May-2011 by Weerasinghe D
Subunit of: photosystem I
Species: Arabidopsis thaliana col
Subunit composition of
photosystem I = [PsaO][PsaG][PsaK][PsaF][PsaH1][PsaL][PsaN][PsaE2][PsaC][PsaD1][PsaA][PsaB]
Photosystem I subunit O = PsaO (summary available)
Photosystem I reaction center subunit V = PsaG (summary available)
Photosystem I reaction center subunit psaK = PsaK (summary available)
Photosystem I reaction center subunit III = PsaF (summary available)
Photosystem I reaction center subunit VI-1 = PsaH1 (summary available)
Photosystem I reaction center subunit XI = PsaL (summary available)
Photosystem I reaction center subunit N = PsaN (summary available)
Photosystem I reaction center subunit IV B = PsaE2 (summary available)
Photosystem I iron-sulfur center = PsaC (summary available)
Photosystem I reaction center subunit II-1 = PsaD1 (summary available)
Photosystem I P700 chlorophyll a apoprotein A1 = PsaA (summary available)
Photosystem I P700 chlorophyll a apoprotein A2 = PsaB (summary available)
PSI is a multiprotein complex of up to 15 core subunits and is trimeric in cyanobacteria [Ozawa10]. In algae and higher plants the PSI core is associated with the peripheral light-harvesting antenna complex I (LHCI) that together form the PSI-LHCI supercomplex [Ozawa10]. PSI is associated with cofactors, such as chlorophyll, a, β carotene, lipid and iron sulfur clusters [Wicke11]. PSI uses solar energy to generate P700 [Webber01]. P700 is the primary electron donor that catalyzes electron transfer from plastocyanin or cytochrome c6 to the intermediate electron acceptors A0, A1 and FX [Sun99]. This culminates in the transfer of an electron to NADP+ to form NADPH via ferredoxin and the associated oxidoreductase.
P700 is a dimer of chlorophyll a and a' stabilized by PsaA and PsaB [Vassiliev95]. This forms the reaction center (RC) at the core of PSI. PsaF and PsaN are involved in docking plastocyanin or cytochrome c6 to the PSI complex and for efficient electron transfer to P700+ [Hippler97]. Two 4[FeS] clusters (FA and FB), the terminal electron acceptors bind to peripheral subunit PsaC, which together with PsaD and PsaE forms the docking site for ferredoxin to the PSI complex on the stromal side [Ozawa10].
PsaG, PsaH, and PsaN are special to eukaryotes and are involved in binding the light harvesting polypeptides. Some newly characterized accessory proteins Inner membrane ALBINO3-like protein 1 and Inner membrane ALBINO3-like protein 2 are crucial in mediating LHC protein integration into the thylakoid membrane [Gohre06].
Chaperone proteins that play a pivotal role in the stepwise integration of PSI subunits into a functional complex have recently been elucidated. These include chloroplast encoded Ycf4 and Ycf3, located in the thylakoid membrane that are required for a posttranslational step of PSI assembly [Albus10].
Locations: chloroplast thylakoid
|Cellular Component:||GO:0009534 - chloroplast thylakoid|
Revised 05-May-2011 by Weerasinghe D
Enzymatic reaction of: photosystem I
EC Number: 220.127.116.11
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.
The reaction is favored in the direction shown.
In Pathways: photosynthesis light reactions
Albus10: Albus CA, Ruf S, Schottler MA, Lein W, Kehr J, Bock R (2010). "Y3IP1, a nucleus-encoded thylakoid protein, cooperates with the plastid-encoded Ycf3 protein in photosystem I assembly of tobacco and Arabidopsis." Plant Cell 22(8);2838-55. PMID: 20807881
Gohre06: Gohre V, Ossenbuhl F, Crevecoeur M, Eichacker LA, Rochaix JD (2006). "One of two alb3 proteins is essential for the assembly of the photosystems and for cell survival in Chlamydomonas." Plant Cell 18(6);1454-66. PMID: 16679460
Hippler97: Hippler M, Drepper F, Farah J, Rochaix JD (1997). "Fast electron transfer from cytochrome c6 and plastocyanin to photosystem I of Chlamydomonas reinhardtii requires PsaF." Biochemistry 36(21);6343-9. PMID: 9174349
Jensen00: Jensen PE, Gilpin M, Knoetzel J, Scheller HV (2000). "The PSI-K subunit of photosystem I is involved in the interaction between light-harvesting complex I and the photosystem I reaction center core." J Biol Chem 2000;275(32);24701-8. PMID: 10818090
Ozawa10: Ozawa S, Onishi T, Takahashi Y (2010). "Identification and characterization of an assembly intermediate subcomplex of photosystem I in the green alga Chlamydomonas reinhardtii." J Biol Chem 285(26);20072-9. PMID: 20413595
Sun99: Sun J, Xu W, Hervas M, Navarro JA, Rosa MA, Chitnis PR (1999). "Oxidizing side of the cyanobacterial photosystem I. Evidence for interaction between the electron donor proteins and a luminal surface helix of the PsaB subunit." J Biol Chem 274(27);19048-54. PMID: 10383406
vanThor99: van Thor JJ, Geerlings TH, Matthijs HC, Hellingwerf KJ (1999). "Kinetic evidence for the PsaE-dependent transient ternary complex photosystem I/Ferredoxin/Ferredoxin:NADP(+) reductase in a cyanobacterium." Biochemistry 38(39);12735-46. PMID: 10504244
Varotto00: Varotto C, Pesaresi P, Meurer J, Oelmuller R, Steiner-Lange S, Salamini F, Leister D (2000). "Disruption of the Arabidopsis photosystem I gene psaE1 affects photosynthesis and impairs growth." Plant J 2000;22(2);115-24. PMID: 10792827
Vassiliev95: Vassiliev IR, Jung YS, Smart LB, Schulz R, McIntosh L, Golbeck JH (1995). "A mixed-ligand iron-sulfur cluster (C556SPaB or C565SPsaB) in the Fx-binding site leads to a decreased quantum efficiency of electron transfer in photosystem I." Biophys J 69(4);1544-53. PMID: 8534825
Wicke11: Wicke S, Schneeweiss GM, dePamphilis CW, Muller KF, Quandt D (2011). "The evolution of the plastid chromosome in land plants: gene content, gene order, gene function." Plant Mol Biol 76(3-5);273-97. PMID: 21424877
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