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Photosynthetic reaction center protein family



Photosynthetic reaction centre protein
Identifiers
Symbol Photo_RC
Pfam PF00124
InterPro IPR000484
SCOP 1prc
TCDB 3.E.2
OPM family 2
OPM protein 1dxr
Available PDB structures:

1cltM:37-306 4prcM:37-306 1r2cM:37-306 1prcM:37-306 5prcM:37-306 1vrnM:37-306 3prcM:37-306 2prcM:37-306 6prcM:37-306 7prcM:37-306 1dxrM:37-306 1dopA:105-296 2axtA:28-330 1s5lD:28-327

Photosynthetic reaction centre proteins are main protein components of photosynthetic reaction centers of bacteria and plants.

Additional recommended knowledge

Contents

In bacteria

The photosynthetic apparatus in non-oxygenic bacteria consists of light-harvesting protein-pigment complexes LH1 and LH2, which use carotenoid and bacteriochlorophyll as primary donors[1]. LH1 acts as the energy collection hub, temporarily storing it before its transfer to the photosynthetic reaction ce ntre (RC)[2]. Electrons are transferred from the primary donor via an intermediate acceptor (bacteriopheophytin) to the primary acceptor (quinine Qa), and finally to the secondary acceptor (quinone Qb), resulting in the formation of ubiquinol QbH2. RC uses the excitation energy to shuffle electrons across the membrane, transferring them via ubiquinol to the cytochrome bc1 complex in order to establish a proton gradient across the membrane, which is used by ATP synthetase to form ATP[3][4][5].

The core complex is anchored in the cell membrane, consisting of one unit of RC surrounded by LH1; in some species there may be additional subunits[6]. RC consists of three subunits: L (light), M (medium), and H (heavy). Subunits L and M provide the scaffolding for the chromophore, while subunit H contains a cytoplasmic domain[7]. In Rhodopseudomonas viridis, there is also a non-membranous tetrahaem cytochrome (4Hcyt) subunit on the periplasmic surface.

In plant photosystems

This entry describes the photosynthetic reaction centre L and M subunits, and the homologous D1 (PsbA) and D2 (PsbD) photosystem II (PSII) reaction centre proteins from cyanobacteria, algae and plants. The D1 and D2 proteins only show approximately 15% sequence homology with the L and M subunits, however the conserved amino acids correspond to the binding sites of the phytochemically active cofactors. As a result, the reaction centres (RCs) of purple photosynthetic bacteria and PSII display considerable structural similarity in terms of cofactor organisation.

The D1 and D2 proteins occur as a heterodimer that form the reaction core of PSII, a multisubunit protein-pigment complex containing over forty different cofactors, which are anchored in the cell membrane in cyanobacteria, and in the thylakoid membrane in algae and plants. Upon absorption of light energy, the D1/D2 heterodimer undergoes charge separation, and the electrons are transferred from the primary donor (chlorophyll a) via pheophytin to the primary acceptor quinone Qa, then to the secondary acceptor Qb, which like the bacterial system, culminates in the production of ATP. However, PSII has an additional function over the bacterial system. At the oxidising side of PSII, a redox-active residue in the D1 protein reduces P680, the oxidised tyrosine then withdrawing electrons from a manganese cluster, which in turn withdraw electrons from water, leading to the splitting of water and the formation of molecular oxygen. PSII thus provides a source of electrons that can be used by photosystem I to produce the reducing power (NADPH) required to convert CO2 to glucose[8][9].

References

  1. ^ Michel H, Oesterhelt D, Lancaster CR, Bibikova MV, Sabatino P (2000). "Structural basis of the drastically increased initial electron transfer rate in the reaction center from a Rh odopseudomonas viridis mutant described at 2.00-A resolution". J. Biol. Chem. 275 (50): 39364-39368. PMID 11005826.
  2. ^ Hunter CN, Bullough PA, Otto C, Bahatyrova S, Frese RN, Siebert CA, Olsen JD, Van Der Werf KO, Van Grondelle R, Niederman RA (2004). "The native architecture of a photosynthetic membrane". Nature 430 (7003): -. PMID 15329728.
  3. ^ Scheuring S (2006). "AFM studies of the supramolecular assembly of bacterial photosynthetic core-complexes". Curr Opin Chem Biol 10 (5): -. PMID 16931113.
  4. ^ Remy A, GerwertK (2003). "Coupling of light-induced electron transfer to proton uptake in photosynthesis". Nat. Struct. Biol. 10 (8): 637-644. PMID 12872158.
  5. ^ Michel H, Deisenhofer J (1989). "Nobel lecture. The photosynthetic reaction centre from the purple bacterium Rhodopseudomonas viridis". EMBO J. 8 (8): 2149-2170. PMID 2676514.
  6. ^ Miki K, Kobayashi M, Nogi T, Fathir I, Nozawa T (2000). "Crystal structures of photosynthetic reaction center and high-potential iron-sulfur protein from Thermochromatium tepidum: thermostability and electron transfer". Proc. Natl. Acad. Sci. U.S.A. 97 (25): 13561-13566. PMID 11095707.
  7. ^ Michel H, Ermler U, Schiffer M (1994). "Structure and function of the photosynthetic reaction center from Rhodobacter sphaeroides". J. Bioenerg. Biomembr. 26 (1): -. PMID 8027023.
  8. ^ Kamiya N, Shen JR (2003). "Crystal structure of oxygen-evolving photosystem II from Thermosynechococcus vulcanus at 3.7-A resolution". Proc. Natl. Acad. Sci. U.S.A. 100 (1): 98-103. PMID 12518057.
  9. ^ Schroder WP, Shi LX (2004). "The low molecular mass subunits of the photosynthetic supracomplex, photosystem II". Biochim. Biophys. Acta 1608 (2-3): 75-96. PMID 14871485.


Subfamilies

  • Photosynthetic reaction centre, M subunit IPR005781
  • Photosystem II reaction centre protein PsbA/D1 IPR005867
  • Photosystem II reaction centre protein PsbD/D2 IPR005868
  • Photosynthetic reaction centre, L subunit IPR005871

References

  • [1]. X-ray structure analysis of a membrane protein complex. Electron density map at 3 A resolution and a model of the chromophores of the photosynthetic reaction center from Rhodopseudomonas viridis. Deisenhofer J, Epp O, Miki K, Huber R, Michel H; J Mol Biol 1984;180:385-398. PubMed
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Photosynthetic_reaction_center_protein_family". A list of authors is available in Wikipedia.
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