Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
twitter

MetaCyc Enzyme: photosystem II

Synonyms: PS II

Species: Synechococcus elongatus PCC 7942

Subunit composition of photosystem II = [(PsbX)(PsbW)(PsbV)(PsbL)(PsbK)(PsbJ)(PsbI)(PsbU)(PsbT)(PsbO)(PsbN)(PsbM)(PsbH)(PsbC)(PsbB)([(PsbE)2][(PsbF)2])([PsbA1][PsbD1])]2
         photosystem II monomer = (PsbX)(PsbW)(PsbV)(PsbL)(PsbK)(PsbJ)(PsbI)(PsbU)(PsbT)(PsbO)(PsbN)(PsbM)(PsbH)(PsbC)(PsbB)([(PsbE)2][(PsbF)2])([PsbA1][PsbD1])
                 Photosystem II reaction center X protein = PsbX (summary available)
                 Photosystem II reaction center psb28 protein = PsbW (summary available)
                 cytochrome c550 = PsbV (summary available)
                 Photosystem II reaction center protein L = PsbL (summary available)
                 Photosystem II reaction center protein K = PsbK (summary available)
                 Photosystem II reaction center protein J = PsbJ (summary available)
                 Photosystem II reaction center protein I = PsbI (summary available)
                 Photosystem II 12 kDa extrinsic protein = PsbU (summary available)
                 Photosystem II reaction center protein T = PsbT (summary available)
                 Photosystem II manganese-stabilizing polypeptide = PsbO (summary available)
                 Protein psbN = PsbN
                 Photosystem II reaction center protein M = PsbM (summary available)
                 Photosystem II reaction center protein H = PsbH
                 Photosystem II 44 kDa reaction center protein = PsbC (summary available)
                 Photosystem II CP47 chlorophyll apoprotein = PsbB (summary available)
                 cytochrome b559 = ([PsbE]2)([PsbF]2)
                         Cytochrome b559 α subunit dimer = (PsbE)2 (summary available)
                                 Cytochrome b559 subunit α = PsbE
                         Cytochrome b559 subunit β = (PsbF)2 (summary available)
                 D1/D2 reaction center complex = (PsbA1)(PsbD1) (summary available)
                         D1 protein = PsbA1 (summary available)
                         D2 protein = PsbD1 (extended summary available)

Summary:
photosystem II (PSII) is a multiprotein complex contained within the thylakoid membranes of plants, algae and cyanobacteria, that utilizes solar energy for splitting water molecules. This reaction is the basis for oxygenic photosynthesis, transferring the electrons via an electron transfer chain that ends with a plastoquinone. This compound donates its electrons to the cytochrome b6f complex, which transfers them to plastocyanin, which in turn transfers the electrons to photosystem I, where they will eventually reduce NADP+ to NADPH. This provides reducing power for biosynthetic reactions and produces molecular oxygen as a by-product.

The heart of the PSII complex consists of the reaction center (RC) core, where light energy is converted into electrochemical potential energy and where the water-splitting reaction occurs. The RC core consists of two homologous proteins known as the D1 protein and D2 protein, which have five transmembrane α-helices each, and four chlorophylls that are associated with them, called P680. Closely associated with the D1/D2 reaction center complex are two chlorophyll-containing proteins, called Photosystem II 44 kDa reaction center protein and Photosystem II CP47 chlorophyll apoprotein. These too are structurally homologous, each having six transmembrane α-helices.

It had been shown that the PSII RC core complex of plants and cyanobacteria is dimeric, having a molecular mass of approx. 700 kDa.

There are many other intrinsic subunits in the complex, including a number of low-molecular mass proteins usually having a single transmembrane helix, which are rather featureless except for the Cytochrome b559 subunit α and PsbF proteins that provide histidine ligands for the high-potential haem of cytochrome b559.

Finally, the PSII RC core complex has several extrinsic proteins attached to its lumenal surface, forming a protein shield over the catalytic site of water splitting. The composition of these proteins is largely species-specific, although Photosystem II manganese-stabilizing polypeptide is found in all oxyphototrophs. In red algae and cyanobacteria, the Photosystem II 12 kDa extrinsic protein and cytochrome c550 proteins associate with Photosystem II manganese-stabilizing polypeptide.

The PSII RC core complex is attached to peripheral light-harvesting systems, which in cyanobacteria and red algae are composed of phycobilins, arranged within the extrinsically located phycobilisomes. There are usually 200-300 light harvesting pigment molecules serving one PSII RC [Barber06]. Most cyanobacteria have distinctly different pigment protein antenna systems, referred to as phycobilisomes [Hankamer01]. These hemidiscoidal structures consist of rod-like arrays of water soluble phycobiliproteins, bound to the stromal surface of the PSII core by linker proteins. The rods are composed of discs that are hexamers of αβ monomers. Each αβ monomer covalently binds two (allophycocyanin) or three (phycocyanin) or more (phycoerythrin) open chain tetrapyrroles.

Excitation of the RC, via light absorption by chlorophylls in the antenna, drives electron transfer from the cluster of four chlorophylls (P680) that are bound to the D1/D2 reaction center complex to a pheophytin acceptor, resulting in a P680* radical. This results in electron transfer activities both downstream and upstream of P680*.

The downstream flow starts with the transfer of the P680* electron to a firmly bound plastoquinone, called QA, and on to a second plastoquinone, named QB. When QB is fully reduced and protonated to plastoquinol (PQH2), it diffuses from the QB-binding site into the lipid matrix of the membrane, where it travels to deliver its electron to the plastoquinol- plastocyanin reductase (better known as the cytochrome b6f complex), which in turn transfers the electron to plastocyanin that travels to photosystem I, where it delivers the electron.

The upstream flow consists of several electron transfers, that can be summarized as the transfer of electrons from two water moleules to the oxidized form of P680. The P680 radical cation (P680*) has a very high redox potential, estimated to be approx. 1.3 V, which is required to drive the water-splitting reaction. The oxidized form of P680 "pulls" an electron from a tyrosine residue (TyrZ) of the D1 protein, one of the protein components of the reaction center. An electron is then transferred to the tyrosine from a manganese atom which is part of a catalytic site called the oxygen-evolving center (OEC). This site is composed of a cluster of four Mn and one Ca2+ ion. Each time P680 is excited by absorbing a photon, the electron transfer results in the removal of an electron from one of the Mn atoms. When four such cycles have occurred, the OEC is ready to receive the four electrons that are involved in the splitting of two water molecules to form dioxygen.

When the water molecules are split and their electrons are transferred to the OEC, two additional "by-products" are formed - molecular oxygen and protons. This accumulation of protons in the thylakoid lumen results in the build-up of a proton gradient across the memberane, which is utilized by ATP synthase to generate ATP.

Locations: thylakoid

Molecular Weight: 700.0 kD (experimental) [Barber06 ]

Gene-Reaction Schematic: ?

GO Terms:

Cellular Component: GO:0030075 - bacterial thylakoid

Credits:
Created 19-May-2008 by Caspi R , SRI International


Enzymatic reaction of: photosystem II

EC Number: 1.10.3.9

4 hν + 2 a plastoquinone + 2 H2O <=> 2 a plastoquinol + oxygen

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 physiologically favored in the direction shown.

In Pathways: ethylene biosynthesis V (engineered) , 1-butanol autotrophic biosynthesis , oxygenic photosynthesis , photosynthesis light reactions


Subunit of photosystem II: photosystem II monomer

Synonyms: PS II


Subunit of photosystem II monomer: Photosystem II reaction center X protein

Synonyms: PsbX

Gene: psbX Accession Number: SYNPCC7942_2016 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 39 AAs

Molecular Weight: 4.243 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: String:1140.Synpcc7942_2016 , UniProt:Q31LM3

Relationship Links: InterPro:IN-FAMILY:IPR009518 , InterPro:IN-FAMILY:IPR023431 , Pfam:IN-FAMILY:PF06596

Summary:
This protein mediates the binding and/or turnover of quinones at the Q(B) site of Photosystem II.


Subunit of photosystem II monomer: Photosystem II reaction center psb28 protein

Synonyms: PsbW

Gene: psbW Accession Number: SYNPCC7942_2478 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 124 AAs

Molecular Weight: 14.424 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:Q8GIS4 , String:1140.Synpcc7942_2478 , UniProt:Q8GIS4

Relationship Links: InterPro:IN-FAMILY:IPR005610 , Pfam:IN-FAMILY:PF03912 , ProDom:IN-FAMILY:PD012692

Summary:
There seems to be uncetainty whether the psb28 gene or the psbW encode the W protein of PS II.


Subunit of photosystem II monomer: cytochrome c550

Synonyms: PsbV

Gene: psbV Accession Number: SYNPCC7942_2010 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 215 AAs

Molecular Weight: 18.2 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:Q31LM9 , SMR:Q31LM9 , String:1140.Synpcc7942_2010 , UniProt:Q31LM9

Relationship Links: InterPro:IN-FAMILY:IPR009056 , InterPro:IN-FAMILY:IPR016003 , InterPro:IN-FAMILY:IPR017851 , Pfam:IN-FAMILY:PF00034 , Prosite:IN-FAMILY:PS51007

Summary:
One of the components of the cyanobacterial oxygen-evolving complex. Cytochrome c plays a role in the oxygen-evolving complex of photosystem II and covalently binds 1 heme group per subunit.


Subunit of photosystem II monomer: Photosystem II reaction center protein L

Synonyms: PsbL, PSII 5 kDa protein

Gene: psbL Accession Number: SYNPCC7942_1175 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 40 AAs

Molecular Weight: 4.575 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:Q8KPP1 , SMR:Q8KPP1 , String:1140.Synpcc7942_1175 , UniProt:Q8KPP1

Relationship Links: InterPro:IN-FAMILY:IPR003372 , Pfam:IN-FAMILY:PF02419

Summary:
The Photosystem II reaction center protein L, Photosystem II reaction center protein M and Photosystem II reaction center protein T proteins, located at the monomer- monomer interface, and may play a role in the dimerization of the PSII complex [Barber06].


Subunit of photosystem II monomer: Photosystem II reaction center protein K

Synonyms: PsbK

Gene: psbK Accession Number: SYNPCC7942_0456 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 45 AAs

Molecular Weight: 5.046 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:Q79AV1 , SMR:Q79AV1 , String:1140.Synpcc7942_0456 , UniProt:Q79AV1

Relationship Links: InterPro:IN-FAMILY:IPR003687 , Pfam:IN-FAMILY:PF02533

Summary:
This protein is a component of the reaction center of photosystem II.


Subunit of photosystem II monomer: Photosystem II reaction center protein J

Synonyms: PsbJ

Gene: psbJ Accession Number: SYNPCC7942_1174 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 39 AAs

Molecular Weight: 3.842 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:Q8KPP0 , SMR:Q8KPP0 , String:1140.Synpcc7942_1174 , UniProt:Q8KPP0

Relationship Links: InterPro:IN-FAMILY:IPR002682 , Pfam:IN-FAMILY:PF01788

Summary:
This protein is a component of the reaction center of photosystem II.


Subunit of photosystem II monomer: Photosystem II reaction center protein I

Synonyms: PsbI

Gene: psbI Accession Number: SYNPCC7942_1705 (MetaCyc)

Sequence Length: 39 AAs

Molecular Weight: 4.392 kD (from nucleotide sequence)

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:Q31MI4 , SMR:Q31MI4 , String:1140.Synpcc7942_1705 , UniProt:Q31MI4

Relationship Links: InterPro:IN-FAMILY:IPR003686 , Pfam:IN-FAMILY:PF02532

Summary:
This protein is a component of the reaction center of photosystem II .


Subunit of photosystem II monomer: Photosystem II 12 kDa extrinsic protein

Synonyms: PsbU, PSII-U, PS II complex 12 kDa extrinsic protein

Gene: psbU Accession Number: SYNPCC7942_1882 (MetaCyc)

Sequence Length: 136 AAs

Molecular Weight: 15.066 kD (from nucleotide sequence)

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:Q31M07 , String:1140.Synpcc7942_1882 , UniProt:Q31M07

Relationship Links: InterPro:IN-FAMILY:IPR010527 , InterPro:IN-FAMILY:IPR018944 , Pfam:IN-FAMILY:PF06514

Summary:
This protein strengthens the structure of the PSII oxygen-evolving complex (OEC), and protects the OEC from heat-induced inactivation.


Subunit of photosystem II monomer: Photosystem II reaction center protein T

Synonyms: PsbT

Gene: psbT Accession Number: SYNPCC7942_0696 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 31 AAs

Molecular Weight: 3.53 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:Q31QE1 , SMR:Q31QE1 , String:1140.Synpcc7942_0696 , UniProt:Q31QE1

Relationship Links: InterPro:IN-FAMILY:IPR001743 , Pfam:IN-FAMILY:PF01405

Summary:
The Photosystem II reaction center protein L, Photosystem II reaction center protein M and Photosystem II reaction center protein T proteins, located at the monomer- monomer interface, may play a role in the dimerization of the PSII complex [Barber06].


Subunit of photosystem II monomer: Photosystem II manganese-stabilizing polypeptide

Synonyms: WoxA, PsbO

Gene: psbO Accession Number: SYNPCC7942_0294 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 277 AAs

Molecular Weight: 29.304 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:P11472 , SMR:P11472 , String:1140.Synpcc7942_0294 , UniProt:P11472

Relationship Links: InterPro:IN-FAMILY:IPR002628 , InterPro:IN-FAMILY:IPR011250 , Pfam:IN-FAMILY:PF01716

Summary:
This is a monomer that binds to a putative Mn-binding protein and contains two of the four Mn-atoms associated with PSII.

Citations: [Kuwabara87, Kuwabara89]


Subunit of photosystem II monomer: Protein psbN

Synonyms: PsbN

Gene: psbN Accession Number: SYNPCC7942_0224 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 46 AAs

Molecular Weight: 4.988 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Unification Links: String:1140.Synpcc7942_0224 , UniProt:Q31RR3

Relationship Links: InterPro:IN-FAMILY:IPR003398 , Pfam:IN-FAMILY:PF02468 , ProDom:IN-FAMILY:PD005510


Subunit of photosystem II monomer: Photosystem II reaction center protein M

Synonyms: PsbM

Gene: psbM Accession Number: SYNPCC7942_0699 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 35 AAs

Molecular Weight: 3.911 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:Q31QD8 , SMR:Q31QD8 , String:1140.Synpcc7942_0699 , UniProt:Q31QD8

Relationship Links: InterPro:IN-FAMILY:IPR007826 , Pfam:IN-FAMILY:PF05151

Summary:
The Photosystem II reaction center protein L, Photosystem II reaction center protein M and Photosystem II reaction center protein T proteins, located at the monomer- monomer interface, may play a role in maintaining the dimerization of the PSII complex [Barber06].


Subunit of photosystem II monomer: Photosystem II reaction center protein H

Synonyms: PsbH

Gene: psbH Accession Number: SYNPCC7942_0225 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 67 AAs

Molecular Weight: 7.62 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Unification Links: Protein Model Portal:Q31RR2 , SMR:Q31RR2 , String:1140.Synpcc7942_0225 , UniProt:Q31RR2

Relationship Links: InterPro:IN-FAMILY:IPR001056 , Pfam:IN-FAMILY:PF00737 , ProDom:IN-FAMILY:PD003584


Subunit of photosystem II monomer: Photosystem II 44 kDa reaction center protein

Synonyms: PsbC, PSII 43 kDa protein, Protein CP-43, Protein P6

Gene: psbC Accession Number: SYNPCC7942_0656 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 461 AAs

Molecular Weight: 50.14 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:P11004 , SMR:P11004 , String:1140.Synpcc7942_0656 , UniProt:P11004

Relationship Links: InterPro:IN-FAMILY:IPR000932 , InterPro:IN-FAMILY:IPR005869 , Pfam:IN-FAMILY:PF00421

Summary:
Photosystem II 44 kDa reaction center protein binds 14 chlorophylls, which are arranged in layers towards the lumenal and stromal surfaces. The majority of the Chls bound to Photosystem II 44 kDa reaction center protein and Photosystem II CP47 chlorophyll apoprotein have counterparts bound in the amino terminal domains of PsaA and PsaB reaction center proteins of photosystem I [Barber06].


Subunit of photosystem II monomer: Photosystem II CP47 chlorophyll apoprotein

Synonyms: PsbB, Protein CP-47

Gene: psbB Accession Number: SYNPCC7942_0697 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 508 AAs

Molecular Weight: 55.766 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:P31094 , SMR:P31094 , String:1140.Synpcc7942_0697 , UniProt:P31094

Relationship Links: InterPro:IN-FAMILY:IPR000932 , InterPro:IN-FAMILY:IPR017486 , Pfam:IN-FAMILY:PF00421

Summary:
This protein binds chlorophyll and catalyzes the primary light-induced photochemical processes of PSII.

Photosystem II CP47 chlorophyll apoprotein binds 16 chlorophylls which are arranged in layers towards the lumenal and stromal surfaces. The majority of the chlorophylls bound to Photosystem II 44 kDa reaction center protein and Photosystem II CP47 chlorophyll apoprotein have counterparts bound in the amino terminal domains of PsaA and PsaB reaction center proteins of photosystem I [Barber06].


Subunit of photosystem II monomer: cytochrome b559


Subunit of cytochrome b559: Cytochrome b559 α subunit dimer

Synonyms: PSII reaction center subunit V

Gene: psbE Accession Number: SYNPCC7942_1177 (MetaCyc)

Locations: thylakoid membrane

Subunit composition of Cytochrome b559 α subunit dimer = [PsbE]2
         Cytochrome b559 subunit α = PsbE

Map Position: [1,209,715 <- 1,209,966]

Molecular Weight of Polypeptide: 9.334 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:Q8KPP3 , SMR:Q8KPP3 , String:1140.Synpcc7942_1177 , UniProt:Q8KPP3

Relationship Links: InterPro:IN-FAMILY:IPR006216 , InterPro:IN-FAMILY:IPR006217 , InterPro:IN-FAMILY:IPR013081 , InterPro:IN-FAMILY:IPR013082 , Pfam:IN-FAMILY:PF00283 , Pfam:IN-FAMILY:PF00284 , Prosite:IN-FAMILY:PS00537

Summary:
Part of a complex consisting of an α and β subunit heterodimer. This b-type cytochrome is tightly associated with the reaction center of photosystem II and may be part of the water-oxidation complex.


Subunit of cytochrome b559: Cytochrome b559 subunit β

Synonyms: cytochrome b559 β subunit, PSII reaction center subunit VI

Gene: psbF Accession Number: SYNPCC7942_1176 (MetaCyc)

Locations: thylakoid membrane

Subunit composition of Cytochrome b559 subunit β = [PsbF]2

Map Position: [1,209,559 <- 1,209,693]

Molecular Weight of Polypeptide: 4.925 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:Q8KPP2 , SMR:Q8KPP2 , String:1140.Synpcc7942_1176 , UniProt:Q8KPP2

Relationship Links: InterPro:IN-FAMILY:IPR006216 , InterPro:IN-FAMILY:IPR006241 , InterPro:IN-FAMILY:IPR013081 , Pfam:IN-FAMILY:PF00283 , Prosite:IN-FAMILY:PS00537

Summary:
Part of a complex consisting of an α and β subunit heterodimer. This b-type cytochrome is tightly associated with the reaction center of PSII and may be part of the water-oxidation complex.


Subunit of photosystem II monomer: D1/D2 reaction center complex

Summary:
The D1 and D2 proteins contain the cofactors that bring about charge separation, leading to the oxidation of water and reduction of the terminal electron/proton acceptor, a plastoquinone. Together, they bind six chlorophyll amolecules, two pheophytin molecules, two plastoquinones, one α-carotene on the D2 side of the RC, one α-carotene on the D1 side, and a non-haem iron [Loll05, Barber06].


Subunit of D1/D2 reaction center complex: D1 protein

Synonyms: photosystem II D1 protein

Gene: psbA1 Accession Number: SYNPCC7942_0424 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 360 AAs

Molecular Weight: 39.965 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Unification Links: Protein Model Portal:P04996 , SMR:P04996 , String:1140.Synpcc7942_0424 , UniProt:P04996

Relationship Links: InterPro:IN-FAMILY:IPR000484 , InterPro:IN-FAMILY:IPR005867 , Pfam:IN-FAMILY:PF00124 , Prints:IN-FAMILY:PR00256 , Prosite:IN-FAMILY:PS00244

Summary:
Similar to higher plants, cyanobacteria utilize two photosystems to perform oxygenic photosynthesis [Oren77]. These are thylakoid membrane protein complexes composed of a number of polypeptide components [Golden86].

The heart of the PSII complex is the reaction center (RC) core, where light energy is converted into electrochemical potential energy and where the water-splitting reaction occurs. The RC core consists of two homologous proteins known as D1 and D2 that form a heterodimer, which have five transmembrane α-helices each [Rhee01]. These proteins bind several cofactors that facilitate primary charge separation, and are closely associated with two chlorophyll-containing proteins (CPs) called CP43 and CP47 [Barber06].

The product of the psbA gene is the D1 protein. The Synechococcus elongatus PCC 7942 genome contains three copies of this gene -psbA1, psbA2 and psbA3.


Subunit of D1/D2 reaction center complex: D2 protein

Synonyms: photosystem II D2 protein

Gene: psbD1 Accession Number: SYNPCC7942_0655 (MetaCyc)

Locations: thylakoid membrane

Sequence Length: 352 AAs

Molecular Weight: 39.446 kD (from nucleotide sequence)

GO Terms:

Cellular Component: GO:0042651 - thylakoid membrane

Gene Class: UNCLASSIFIED

Relationship Links: UniProt:PART-OF:P11005

Summary:
Similar to higher plants, cyanobacteria utilize two photosystems to perform oxygenic photosynthesis [Oren77]. These are thylakoid membrane protein complexes composed of a number of polypeptide components.

The heart of the PSII complex is the reaction center (RC) core, where light energy is converted into electrochemical potential energy and where the water-splitting reaction occurs. The RC core consists of two homologous proteins known as D1 and D2 that form a heterodimer and which have five transmembrane α-helices each [Rhee01]. These proteins bind several cofactors that facilitate primary charge separation, and are closely associated with two chlorophyll-containing proteins (CPs) called CP43 and CP47 [Barber06].

The product of the psbD gene is the D2 protein, also known as the QA protein. This protein is essential for oxygenic photosynthetic electron transport. The Synechococcus elongatus PCC 7942 genome contains two copies of this gene -psbD1 and psbD2. The two genes encode identical polypeptides [Golden88].


References

Barber06: Barber J (2006). "Photosystem II: an enzyme of global significance." Biochem Soc Trans 34(Pt 5);619-31. PMID: 17052167

Collins81: Collins MD, Jones D (1981). "Distribution of isoprenoid quinone structural types in bacteria and their taxonomic implication." Microbiol Rev 45(2);316-54. PMID: 7022156

Golden86: Golden SS, Brusslan J, Haselkorn R (1986). "Expression of a family of psbA genes encoding a photosystem II polypeptide in the cyanobacterium Anacystis nidulans R2." EMBO J 5(11);2789-98. PMID: 3098559

Golden88: Golden SS, Stearns GW (1988). "Nucleotide sequence and transcript analysis of three photosystem II genes from the cyanobacterium Synechococcus sp. PCC7942." Gene 67(1);85-96. PMID: 3138165

Hankamer01: Hankamer B, Morris E, Nield J, Carne A, Barber J (2001). "Subunit positioning and transmembrane helix organisation in the core dimer of photosystem II." FEBS Lett 504(3);142-51. PMID: 11532446

Kuwabara87: Kuwabara T, Reddy KJ, Sherman LA (1987). "Nucleotide sequence of the gene from the cyanobacterium Anacystis nidulans R2 encoding the Mn-stabilizing protein involved in photosystem II water oxidation." Proc Natl Acad Sci U S A 84(23);8230-4. PMID: 3120187

Kuwabara89: Kuwabara T, Nagata R, Shinohara K (1989). "Expression and processing of cyanobacterial Mn-stabilizing protein in Escherichia coli." Eur J Biochem 186(1-2);227-32. PMID: 2689172

Loll05: Loll B, Kern J, Saenger W, Zouni A, Biesiadka J (2005). "Towards complete cofactor arrangement in the 3.0 A resolution structure of photosystem II." Nature 438(7070);1040-4. PMID: 16355230

Oren77: Oren A, Padan E, Avron M (1977). "Quantum yields for oxygenic and anoxygenic photosynthesis in the cyanobacterium Oscillatoria limnetica." Proc Natl Acad Sci U S A 74(5);2152-6. PMID: 16592398

Rhee01: Rhee KH (2001). "Photosystem II: the solid structural era." Annu Rev Biophys Biomol Struct 30;307-28. PMID: 11340062


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 Fri Nov 28, 2014, BIOCYC13B.