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MetaCyc Polypeptide: Photosystem I reaction center subunit XII

Gene: psaM Accession Number: G-406 (MetaCyc)

Synonyms: PSI-M

Species: Synechocystis sp. PCC 6803

Component of:
photosystem I complex
photosystem I (extended summary available)

Summary:
PsaM coordinates one chlorophyll a and this may play a role in the transfer of excitation energy between monomers [Grotjohann05]. It also mediates hydrophobic contacts with a carotenoid molecule [Grotjohann05].

Locations: thylakoid membrane

Molecular Weight of Polypeptide: 3.38 kD (from nucleotide sequence)

Unification Links: KEGG:smr0005 , Protein Model Portal:P72986 , SMR:P72986 , String:1148.smr0005 , UniProt:P72986

Relationship Links: InterPro:IN-FAMILY:IPR010010 , Pfam:IN-FAMILY:PF07465

Gene-Reaction Schematic: ?

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Credits:
Revised 04-May-2011 by Weerasinghe D


Subunit of: photosystem I complex

Species: Synechocystis sp. PCC 6803

Subunit composition of photosystem I complex = [(PsaA)(PsaB)][PsaC][PsaD][PsaE][PsaF][PsaL][PsaJ][PsaK1][PsaL][PsaM][PsaK2]
         P700 protein = (PsaA)(PsaB) (summary available)
                 Photosystem I P700 chlorophyll a apoprotein A1 = PsaA (summary available)
                 Photosystem I P700 chlorophyll a apoprotein A2 = PsaB (summary available)
         Photosystem I iron-sulfur center = PsaC (summary available)
         Photosystem I reaction center subunit II = PsaD (summary available)
         Photosystem I reaction center subunit IV = PsaE (summary available)
         Photosystem I reaction center subunit III = PsaF (summary available)
         Photosystem I reaction center subunit VIII = PsaL (summary available)
         Photosystem I reaction center subunit IX = PsaJ (summary available)
         Photosystem I reaction center subunit PsaK 1 = PsaK1 (summary available)
         Photosystem I reaction center subunit XI = PsaL (summary available)
         Photosystem I reaction center subunit XII = PsaM (summary available)
         Photosystem I reaction center subunit PsaK 2 = PsaK2 (summary available)

Component of: photosystem I (extended summary available)


Subunit of: photosystem I

Synonyms: photosystem I trimer complex

Species: Synechocystis sp. PCC 6803

Subunit composition of photosystem I = [([PsaA][PsaB])(PsaC)(PsaD)(PsaE)(PsaF)(PsaL)(PsaJ)(PsaK1)(PsaL)(PsaM)(PsaK2)]3
         photosystem I complex = ([PsaA][PsaB])(PsaC)(PsaD)(PsaE)(PsaF)(PsaL)(PsaJ)(PsaK1)(PsaL)(PsaM)(PsaK2)
                 P700 protein = (PsaA)(PsaB) (summary available)
                         Photosystem I P700 chlorophyll a apoprotein A1 = PsaA (summary available)
                         Photosystem I P700 chlorophyll a apoprotein A2 = PsaB (summary available)
                 Photosystem I iron-sulfur center = PsaC (summary available)
                 Photosystem I reaction center subunit II = PsaD (summary available)
                 Photosystem I reaction center subunit IV = PsaE (summary available)
                 Photosystem I reaction center subunit III = PsaF (summary available)
                 Photosystem I reaction center subunit VIII = PsaL (summary available)
                 Photosystem I reaction center subunit IX = PsaJ (summary available)
                 Photosystem I reaction center subunit PsaK 1 = PsaK1 (summary available)
                 Photosystem I reaction center subunit XI = PsaL (summary available)
                 Photosystem I reaction center subunit XII = PsaM (summary available)
                 Photosystem I reaction center subunit PsaK 2 = PsaK2 (summary available)

Summary:
Photosystem I (PS I) is a large membrane protein complex that catalyzes the light driven electron transfer from plastocyanin, which is located on the inside of the thylakoids (the lumen), to ferredoxin, which is on the stromal side of the membrane.

Cyanobacterial PS I can exist in both trimeric and monomeric forms. The trimeric form has been shown to be the prominent oligomeric state at low light intensity. The monomeric unit of PSI from Synechocystis sp. PCC 6803 consists of 11 protein subunits, to which 127 cofactors are non-covalently bound. The 12 proteins are Photosystem I P700 chlorophyll a apoprotein A1, Photosystem I P700 chlorophyll a apoprotein A2, Photosystem I iron-sulfur center, Photosystem I reaction center subunit II, Photosystem I reaction center subunit IV, Photosystem I reaction center subunit III, Photosystem I reaction center subunit IX, Photosystem I reaction center subunit IX, Photosystem I reaction center subunit PsaK 1, Photosystem I reaction center subunit XI, Photosystem I reaction center subunit XII. Some thermophilic cyanobacteria may contain an additional subunit, PsaX.

The processes catalyzed by Photosystem I can be divided into:

1. light capturing and excitation energy transfer

2. electron transfer.

The light capturing is performed by the large antenna system that consists of 90 antenna chlorophylls and 22 carotenoids. The excitation energy is transferred to the center of the complex, where the electron transport chain is located. The electron transport chain consists of six chlorophylls, two phylloquinones and three 4Fe4S clusters.

The charge separation is initiated from the P700 protein, the electron donor, which consists of a heterodimer of a chlorophyll a and a chlorophyll a' (the C13 epimer of chlorophyll a). From P700, the electron is transferred stepwise to A (a chlorophyll a molecule), A0 (also a chlorophyll a molecule), A1 (a phylloquinone molecule) and from there subsequently to the three a [4Fe-4S] iron-sulfur cluster, named FX, FA and FB. After the docking of ferredoxin, the electron is transferred from the terminal 4Fe4S cluster of PS I, FB, to the 2Fe2S cluster of ferredoxin, which transfers the electron to the ferredoxin-NADP oxidoreductase, where NADP+ is finally reduced to NADPH. Under conditions of iron limitation, a flavodoxin may replace the ferredoxin [Grotjohann05].

P700 is re-reduced with the electrons delivered from photosystem II by plastocyanin.

Credits:
Created 04-Jan-1999 by Zhang P , TAIR
Revised 23-May-2008 by Caspi R , SRI International


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: ethylene biosynthesis V (engineered) , photosynthetic 3-hydroxybutyrate biosynthesis (engineered) , oxygenic photosynthesis , photosynthesis light reactions


References

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

Park06: Park YJ, Yoo CB, Choi SY, Lee HB (2006). "Purifications and characterizations of a ferredoxin and its related 2-oxoacid:ferredoxin oxidoreductase from the hyperthermophilic archaeon, Sulfolobus solfataricus P1." J Biochem Mol Biol 39(1);46-54. PMID: 16466637


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 18.5 on Sun Dec 21, 2014, BIOCYC13A.