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MetaCyc Polypeptide: Photosystem I P700 chlorophyll a apoprotein A2

Gene: psaB Accession Number: CHRECP048 (MetaCyc)

Synonyms: ChreCp048, PSI-B

Species: Chlamydomonas reinhardtii

Component of:
photosystem I (extended summary available)
PS I-LHCI supercomplex (summary available)

Summary:
PSI consists of a core complex that captures photons, and an electron transfer chain that converts photon excitation into a charge separation. This transfers an electron from the donor P700 to the acceptors A0, A1, FX, FA and FB in turn.

The subunits PSI-A and PSI-B binds to P700 at the reaction center, the heart of PSI [Scheller01]. The PSI-A/B heterodimer can be isolated as a complex known as chlorophyll a-complex 1 (CP1) and contains most of the pigments of PSI [Scheller01].


MapMan: 1.1.2.2 PS.lightreaction.photosystem I.PSI polypeptide subunits
ProMEX peptides
Encoded in the chloroplast genome.

Citations: [Kuck87, Nozaki00, Dron82, Bingham91, Maul02, Rodday95, Webber96, Redding98, Krabben00, GuergovaKuras01, Nakamura03, Boudreaux01]

Locations: chloroplast

Map Position: [119,601 -> 121,808]

Molecular Weight of Polypeptide: 82.1 kD (from nucleotide sequence)

Unification Links: Entrez-gene:2717038 , Pride:P09144 , Protein Model Portal:P09144 , RefSeq:NP_958404.1 , SMR:P09144 , UniProt:P09144

Relationship Links: InterPro:IN-FAMILY:IPR001280 , InterPro:IN-FAMILY:IPR006244 , InterPro:IN-FAMILY:IPR020586 , Pfam:IN-FAMILY:PF00223 , Prints:IN-FAMILY:PR00257 , Prosite:IN-FAMILY:PS00419 , RefSeq:PART-OF:NC_005353.1

Gene-Reaction Schematic: ?

GO Terms:

Cellular Component: GO:0009507 - chloroplast

MultiFun Terms: metabolism energy production/transport

Credits:
Revised 04-May-2011 by Weerasinghe D


Subunit of: photosystem I

Species: Chlamydomonas reinhardtii

Subunit composition of photosystem I = [PsaO][PsaN][PsaL][PsaK][PsaJ][PsaI][PsaH][PsaG][PsaF][PsaE][PsaD][PsaC][PsaB][PsaA]
         Photosystem I subunit O = PsaO (summary available)
         Photosystem I reaction center subunit N = PsaN (summary available)
         Photosystem I reaction center subunit XI = PsaL (summary available)
         Photosystem I reaction center subunit psaK = PsaK (summary available)
         Photosystem I reaction center subunit IX = PsaJ (summary available)
         Photosystem I reaction centre, subunit VIII = PsaI (summary available)
         Photosystem I reaction center subunit VI = PsaH (summary available)
         Photosystem I reaction center subunit V = PsaG (summary available)
         Photosystem I reaction center subunit III = PsaF (summary available)
         Photosystem I reaction center subunit IV = PsaE (summary available)
         Photosystem I reaction center subunit II = PsaD (summary available)
         Photosystem I iron-sulfur center = PsaC (summary available)
         Photosystem I P700 chlorophyll a apoprotein A2 = PsaB (summary available)
         Photosystem I P700 chlorophyll a apoprotein A1 = PsaA (summary available)

Component of: PS I-LHCI supercomplex (summary available)

Summary:
The function of PSI is to produce the NADPH necessary for the reduction of CO2 in the Calvin-Benson-Bassham cycle.

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].

Credits:
Created 11-Jan-2010 by May P , MPI-MP
Revised 06-May-2011 by Weerasinghe D


Enzymatic reaction of: photosystem I

EC Number: 1.97.1.12

a reduced plastocyanin + an oxidized ferredoxin + hν <=> an oxidized plastocyanin + a reduced ferredoxin

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 , hydrogen production VIII


Enzymatic reaction of: photosystem I

2 NADP+[in] + 2 H+[in] + 4 e- <=> 2 NADPH[in]

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction of enzyme catalysis.

The reaction is favored in the direction shown.


Subunit of: PS I-LHCI supercomplex

Species: Chlamydomonas reinhardtii

Subunit composition of PS I-LHCI supercomplex = [(LHCA3)(LHCA2)][(LHCA4)(LHCA1)][(PsaO)(PsaN)(PsaL)(PsaK)(PsaJ)(PsaI)(PsaH)(PsaG)(PsaF)(PsaE)(PsaD)(PsaC)(PsaB)(PsaA)]
         LHCI-680 = (LHCA3)(LHCA2) (summary available)
                 Light-harvesting chlorophyll-a/b protein of photosystem I = LHCA3 (summary available)
                 Light-harvesting protein of photosystem I = LHCA2 (summary available)
         LHCI-705 = (LHCA4)(LHCA1) (summary available)
                 Light-harvesting protein of photosystem I = LHCA4 (summary available)
                 Light-harvesting protein of photosystem I = LHCA1 (summary available)
         photosystem I = (PsaO)(PsaN)(PsaL)(PsaK)(PsaJ)(PsaI)(PsaH)(PsaG)(PsaF)(PsaE)(PsaD)(PsaC)(PsaB)(PsaA) (extended summary available)
                 Photosystem I subunit O = PsaO (summary available)
                 Photosystem I reaction center subunit N = PsaN (summary available)
                 Photosystem I reaction center subunit XI = PsaL (summary available)
                 Photosystem I reaction center subunit psaK = PsaK (summary available)
                 Photosystem I reaction center subunit IX = PsaJ (summary available)
                 Photosystem I reaction centre, subunit VIII = PsaI (summary available)
                 Photosystem I reaction center subunit VI = PsaH (summary available)
                 Photosystem I reaction center subunit V = PsaG (summary available)
                 Photosystem I reaction center subunit III = PsaF (summary available)
                 Photosystem I reaction center subunit IV = PsaE (summary available)
                 Photosystem I reaction center subunit II = PsaD (summary available)
                 Photosystem I iron-sulfur center = PsaC (summary available)
                 Photosystem I P700 chlorophyll a apoprotein A2 = PsaB (summary available)
                 Photosystem I P700 chlorophyll a apoprotein A1 = PsaA (summary available)

Summary:
The core of the PS I-LHCI supercomplex is formed by the PsaA/B heterodimer with a few small subunits surrounding it, and this core contains all the components necessary for plastocyanin-ferredoxin oxidoreductase activity. All eukaryotic PSI cores characterized so far are monomers [Amunts07]. Except for a few chlorophylls required for the photochemistry, all chlorophylls bound in the core subunits function as light-harvesting pigments. Attached to the core are peripheral light-harvesting antennae composed of several LHCI proteins. Light energy captured by these light-harvesting chlorophylls is delivered to the P700 chlorophyll, where it is trapped as a stable charge separation. Chlamydomonas antenna is composed of LHCI-705 and LHCI-680 subcomplexes formed by Lhca1-4 polypeptides [Bassi92].

Citations: [Jun09]

Locations: chloroplast

GO Terms:

Cellular Component: GO:0009507 - chloroplast

Credits:
Created 12-Jan-2010 by May P , MPI-MP


References

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

Amunts07: Amunts A, Drory O, Nelson N (2007). "The structure of a plant photosystem I supercomplex at 3.4 A resolution." Nature 447(7140);58-63. PMID: 17476261

Bassi92: Bassi R, Soen SY, Frank G, Zuber H, Rochaix JD (1992). "Characterization of chlorophyll a/b proteins of photosystem I from Chlamydomonas reinhardtii." J Biol Chem 267(36);25714-21. PMID: 1464588

Bingham91: Bingham SE, Xu RH, Webber AN (1991). "Transformation of chloroplasts with the psaB gene encoding a polypeptide of the photosystem I reaction center." FEBS Lett 292(1-2);137-40. PMID: 1959594

Boudreaux01: Boudreaux B, MacMillan F, Teutloff C, Agalarov R, Gu F, Grimaldi S, Bittl R, Brettel K, Redding K (2001). "Mutations in both sides of the photosystem I reaction center identify the phylloquinone observed by electron paramagnetic resonance spectroscopy." J Biol Chem 276(40);37299-306. PMID: 11489879

Dron82: Dron M, Rahire M, Rochaix JD (1982). "Sequence of the chloroplast DNA region of Chlamydomonas reinhardii containing the gene of the large subunit of ribulose bisphosphate carboxylase and parts of its flanking genes." J Mol Biol 162(4);775-93. PMID: 6302265

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

Grotjohann05: Grotjohann I, Fromme P (2005). "Structure of cyanobacterial photosystem I." Photosynth Res 85(1);51-72. PMID: 15977059

GuergovaKuras01: Guergova-Kuras M, Boudreaux B, Joliot A, Joliot P, Redding K (2001). "Evidence for two active branches for electron transfer in photosystem I." Proc Natl Acad Sci U S A 98(8);4437-42. PMID: 11274371

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

Jun09: Jun Minagawa (2009). "Light-Harvesting Proteins." Chapter 14. In: The Chlamydomonas Sourcebook. Second Edition.

Krabben00: Krabben L, Schlodder E, Jordan R, Carbonera D, Giacometti G, Lee H, Webber AN, Lubitz W (2000). "Influence of the axial ligands on the spectral properties of P700 of photosystem I: a study of site-directed mutants." Biochemistry 39(42);13012-25. PMID: 11041867

Kuck87: Kuck U, Choquet Y, Schneider M, Dron M, Bennoun P (1987). "Structural and transcription analysis of two homologous genes for the P700 chlorophyll a-apoproteins in Chlamydomonas reinhardii: evidence for in vivo trans-splicing." EMBO J 6(8);2185-95. PMID: 16453785

Maul02: Maul JE, Lilly JW, Cui L, dePamphilis CW, Miller W, Harris EH, Stern DB (2002). "The Chlamydomonas reinhardtii plastid chromosome: islands of genes in a sea of repeats." Plant Cell 14(11);2659-79. PMID: 12417694

Nakamura03: Nakamura A, Akai M, Yoshida E, Taki T, Watanabe T (2003). "Reversed-phase HPLC determination of chlorophyll a' and phylloquinone in Photosystem I of oxygenic photosynthetic organisms. Universal existence of one chlorophyll a' molecule in Photosystem I." Eur J Biochem 270(11);2446-58. PMID: 12755700

Nozaki00: Nozaki H, Misawa K, Kajita T, Kato M, Nohara S, Watanabe MM (2000). "Origin and evolution of the colonial volvocales (Chlorophyceae) as inferred from multiple, chloroplast gene sequences." Mol Phylogenet Evol 17(2);256-68. PMID: 11083939

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

Redding98: Redding K, MacMillan F, Leibl W, Brettel K, Hanley J, Rutherford AW, Breton J, Rochaix JD (1998). "A systematic survey of conserved histidines in the core subunits of Photosystem I by site-directed mutagenesis reveals the likely axial ligands of P700." EMBO J 17(1);50-60. PMID: 9427740

Rodday95: Rodday SM, Webber AN, Bingham SE, Biggins J (1995). "Evidence that the FX domain in photosystem I interacts with the subunit PsaC: site-directed changes in PsaB destabilize the subunit interaction in Chlamydomonas reinhardtii." Biochemistry 34(19);6328-34. PMID: 7756260

Scheller01: Scheller HV, Jensen PE, Haldrup A, Lunde C, Knoetzel J (2001). "Role of subunits in eukaryotic Photosystem I." Biochim Biophys Acta 1507(1-3);41-60. PMID: 11687207

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

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

Webber01: Webber AN, Lubitz W (2001). "P700: the primary electron donor of photosystem I." Biochim Biophys Acta 1507(1-3);61-79. PMID: 11687208

Webber96: Webber AN, Su H, Bingham SE, Kass H, Krabben L, Kuhn M, Jordan R, Schlodder E, Lubitz W (1996). "Site-directed mutations affecting the spectroscopic characteristics and midpoint potential of the primary donor in photosystem I." Biochemistry 35(39);12857-63. PMID: 8841129

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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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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