Editing Photosystem I

{{Short description|Second protein complex in photosynthetic light reactions}}
{{Redirect|PS I|other uses|PSI (disambiguation)|PS1|PlayStation 1}}
[[Image:Thylakoid membrane 3.svg|thumb|400px|right|Light-dependent reactions of photosynthesis at the thylakoid membrane]]
{{Infobox enzyme
| Name       = Photosystem I
| EC_number  = 1.97.1.12
| CAS_number =
| GO_code    = 
| image      = File:PSI+LHC.png
| width      = 
| caption    = Plant photosystem&nbsp;I with LHC I 
}}
[[File:Plastomap of Arabidopsis thaliana.svg|thumb|Location of the ''psa'' genes in the [[chloroplast genome]] of ''[[Arabidopsis thaliana]]''. The 21 protein-coding genes involved in photosynthesis are displayed as green boxes.]]

'''Photosystem&nbsp;I''' ('''PSI''', or '''plastocyanin–ferredoxin oxidoreductase''') is one of two [[photosystem]]s in the [[Light-dependent reactions|photosynthetic light reactions]] of [[algae]], [[plant]]s, and [[cyanobacteria]]. [[Photosystem]]&nbsp;I <ref name="pmid3333014">{{cite journal | vauthors = Golbeck JH | title = Structure, function and organization of the Photosystem I reaction center complex | journal = Biochimica et Biophysica Acta (BBA) - Reviews on Bioenergetics | volume = 895 | issue = 3 | pages = 167–204 | year = 1987 | pmid = 3333014 | doi = 10.1016/s0304-4173(87)80002-2 }}</ref> is an [[integral membrane protein]] [[Protein complex|complex]] that uses [[light]] [[energy]] to catalyze the [[electron transfer|transfer of electrons]] across the [[thylakoid]] membrane from [[plastocyanin]] to [[ferredoxin]]. Ultimately, the electrons that are transferred by Photosystem I are used to produce the moderate-energy hydrogen carrier [[NADPH]].<ref>{{cite journal | vauthors = Yamori W, Shikanai T | title = Physiological Functions of Cyclic Electron Transport Around Photosystem I in Sustaining Photosynthesis and Plant Growth | journal = Annual Review of Plant Biology | volume = 67 | pages = 81–106 | date = April 2016 | pmid = 26927905 | doi = 10.1146/annurev-arplant-043015-112002 | doi-access = free }}</ref> The photon energy absorbed by Photosystem I also produces a [[Chemiosmosis|proton-motive force]] that is used to generate [[adenosine triphosphate|ATP]]. PSI is composed of more than 110 [[Cofactor (biochemistry)|cofactor]]s, significantly more than [[Photosystem II]].<ref name="Nelson_2006">{{cite journal | vauthors = Nelson N, Yocum CF | title = Structure and function of photosystems I and II | journal = Annual Review of Plant Biology | volume = 57 | pages = 521–65 | year = 2006 | pmid = 16669773 | doi = 10.1146/annurev.arplant.57.032905.105350 }}</ref>

== History ==
This photosystem is known as PSI because it was discovered before Photosystem II, although future experiments showed that Photosystem II is actually the first enzyme of the photosynthetic electron transport chain. Aspects of PSI were discovered in the 1950s, but the significance of these discoveries was not yet recognized at the time.<ref name="Fromme">{{cite journal | vauthors = Fromme P, Mathis P | title = Unraveling the photosystem I reaction center: a history, or the sum of many efforts | journal = Photosynthesis Research | volume = 80 | issue = 1–3 | pages = 109–24 | year = 2004 | pmid = 16328814 | doi = 10.1023/B:PRES.0000030657.88242.e1 | bibcode = 2004PhoRe..80..109F | s2cid = 13832448 }}</ref> Louis Duysens first proposed the concepts of Photosystems I and II in 1960, and, in the same year, a proposal by Fay Bendall and Robert Hill assembled earlier discoveries into a coherent theory of serial photosynthetic reactions.<ref name="Fromme"/> Hill and Bendall's hypothesis was later confirmed in experiments conducted in 1961 by the Duysens and Witt groups.<ref name="Fromme"/>

== Components and action ==
Two main subunits of PSI, PsaA and PsaB, are closely related proteins involved in the [[Binding (molecular)|binding]] of the vital electron transfer cofactors P{{sub|700}}, Acc, A{{sub|0}}, A{{sub|1}}, and F{{sub|x}}. PsaA and PsaB are both [[integral membrane proteins]] of 730 to 750 [[amino acid]]s that contain 11 [[transmembrane domain|transmembrane]] segments. A [[4Fe-4S|[4Fe-4S] iron-sulfur cluster]] called F{{sub|x}} is [[Coordination complex|coordinated]] by four [[cysteine]]s; two cysteines are provided each by PsaA and PsaB. The two cysteines in each are proximal and located in a [[turn (biochemistry)|loop]] between the ninth and tenth transmembrane segments. A [[leucine zipper]] [[protein motif|motif]] seems to be present <ref name="pmid2186925">{{cite journal | vauthors = Webber AN, Malkin R | title = Photosystem I reaction-centre proteins contain leucine zipper motifs. A proposed role in dimer formation | journal = FEBS Letters | volume = 264 | issue = 1 | pages = 1–4 | date = May 1990 | pmid = 2186925 | doi = 10.1016/0014-5793(90)80749-9 | s2cid = 42294700 | doi-access =  | bibcode = 1990FEBSL.264....1W }}</ref> [[Upstream and downstream (DNA)|downstream]] of the cysteines and could contribute to dimerisation of PsaA/PsaB. The terminal electron acceptors F{{sub|A}} and F{{sub|B}}, also [4Fe-4S] iron-sulfur clusters, are located in a 9-kDa protein called PsaC that binds to the PsaA/PsaB core near F{{sub|X}}.<ref>{{cite journal | vauthors = Jagannathan B, Golbeck JH | title = Breaking biological symmetry in membrane proteins: the asymmetrical orientation of PsaC on the pseudo-C2 symmetric Photosystem I core | journal = Cellular and Molecular Life Sciences | volume = 66 | issue = 7 | pages = 1257–70 | date = April 2009 | pmid = 19132290 | doi = 10.1007/s00018-009-8673-x | s2cid = 32418758 | pmc = 11131447 }}</ref><ref>{{cite journal | vauthors = Jagannathan B, Golbeck JH | title = Understanding of the binding interface between PsaC and the PsaA/PsaB heterodimer in photosystem I | journal = Biochemistry | volume = 48 | issue = 23 | pages = 5405–16 | date = June 2009 | pmid = 19432395 | doi = 10.1021/bi900243f }}</ref>

{| class="wikitable"
|+ Components of PSI (protein subunits, lipids, pigments, coenzymes, and cofactors).<ref>{{cite journal | vauthors = Saenger W, Jordan P, Krauss N | title = The assembly of protein subunits and cofactors in photosystem I | journal = Current Opinion in Structural Biology | volume = 12 | issue = 2 | pages = 244–54 | date = April 2002 | pmid = 11959504 | doi = 10.1016/S0959-440X(02)00317-2 }}</ref>
|-
! Protein subunits
! Description
|-
| row 2, cell 1| PsaA
| rowspan=2| Related large transmembrane proteins involved in the binding of P700, A0, A1, and Fx. Part of the [[photosynthetic reaction centre protein family]].
|-
| row 3, cell 1|PsaB
|-
| row 4, cell 1|PsaC
| row 4, cell 2|Iron-sulfur center; apoprotein for F<sub>a</sub> and F<sub>b</sub>
|-
| row 5, cell 1|PsaD
| row 5, cell 2|Required for assembly, helps bind ferredoxin. {{InterPro|IPR003685}}
|-
| row 6, cell 1|PsaE
| row 6, cell 2|{{InterPro|IPR003375}}
|-
| row 7, cell 1|PsaI
| row 7, cell 2|May stabilize PsaL. Stabilizes [[Light-harvesting complexes of green plants|light-harvesting complex]] II binding.<ref>{{cite journal |last1=Plöchinger |first1=Magdalena |last2=Torabi |first2=Salar |last3=Rantala |first3=Marjaana |last4=Tikkanen |first4=Mikko |last5=Suorsa |first5=Marjaana |last6=Jensen |first6=Poul-Erik |last7=Aro |first7=Eva Mari |last8=Meurer |first8=Jörg |title=The Low Molecular Weight Protein PsaI Stabilizes the Light-Harvesting Complex II Docking Site of Photosystem I |journal=Plant Physiology |date=September 2016 |volume=172 |issue=1 |pages=450–463 |doi=10.1104/pp.16.00647|pmid=27406169 |pmc=5074619 }}</ref> {{InterPro|IPR001302}}
|-
| row 8, cell 1|PsaJ
| row 8, cell 2| {{InterPro|IPR002615}}
|-
| row 9, cell 1|PsaK
| row 9, cell 2| {{InterPro|IPR035982}}
|-
| row 10, cell 1|PsaL
| row 10, cell 2|{{InterPro|IPR036592}}
|-
| row 11, cell 1|PsaM
| row 11, cell 2|{{InterPro|IPR010010}}
|-
| row 12, cell 1|PsaX
| row 12, cell 2|{{InterPro|IPR012986}}
|-
| row 13, cell 1|[[cytochrome b6f complex|cytochrome ''b<sub>6</sub>f'' complex]]
| row 13, cell 2|Soluble [[protein]]
|-
| row 14, cell 1|F<sub>a</sub>
| row 14, cell 2|From PsaC; In [[electron transport chain]] (ETC) 
|-
| row 15, cell 1|F<sub>b</sub>
| row 15, cell 2|From PsaC; In ETC
|-
| row 16, cell 1|F<sub>x</sub>
| row 16, cell 2|From PsaAB; In ETC
|-
| row 17, cell 1|[[Ferredoxin]]
| row 17, cell 2|Electron carrier in ETC
|-
| row 18, cell 1|[[Plastocyanin]]
| row 18, cell 2|Soluble protein
|-
! [[Lipid]]s
! Description
|-
| row 19, cell 1|MGDG II
| row 19, cell 2|Monogalactosyldiglyceride lipid
|- 
| row 20, cell 1|PG I
| row 20, cell 2|[[Phosphatidylglycerol]] [[phospholipid]]
|-
| row 21, cell 1|PG III
| row 21, cell 2|Phosphatidylglycerol phospholipid
|-
| row 22, cell 1|PG IV
| row 22, cell 2|Phosphatidylglycerol phospholipid
|-
! Pigments
! Description
|-
| row 23, cell 1|[[Chlorophyll]] ''a''
| row 23, cell 2|90 [[pigment]] molecules in antenna system
|-
| row 24, cell 1|Chlorophyll ''a''
| row 24, cell 2|5 pigment molecules in ETC
|-
| row 25, cell 1|Chlorophyll ''a<sub>0</sub>''
| row 25, cell 2|Early electron acceptor of modified chlorophyll in ETC
|-
| row 26, cell 1|Chlorophyll ''a''′
| row 26, cell 2|1 pigment molecule in ETC
|-
| row 27, cell 1|[[beta-Carotene|β-Carotene]]
| row 27, cell 2|22 [[carotenoid]] pigment molecules
|-
! Coenzymes and cofactors
! Description
|-
| row 28, cell 1|Q<sub>K</sub>-A
| row 28, cell 2|Early electron acceptor [[vitamin K1|vitamin K<sub>1</sub>]] [[phylloquinone]] in ETC
|-
| row 29, cell 1|Q<sub>K</sub>-B
| row 29, cell 2|Early electron acceptor vitamin K<sub>1</sub> phylloquinone in ETC
|-
| row 30, cell 1|FNR
| row 30, cell 2|[[Ferredoxin-NADP+ reductase|Ferredoxin-{{chem|NADP|+}} oxidoreductase enzyme]]
|-
| row 31, cell 1|{{chem|Ca|2+}}
| row 31, cell 2|[[Calcium]] ion
|-
| row 32, cell 1|{{chem|Mg|2+}}
| row 32, cell 2|[[Magnesium]] ion
|}

=== Photon ===

[[Photoexcitation]] of the pigment molecules in the antenna complex induces electron and energy transfer.<ref name = "Raven"/>

=== Antenna complex ===

The antenna complex is composed of molecules of [[chlorophyll]] and [[carotenoid]]s mounted on two proteins.<ref name="Taiz">{{cite book |last1=Zeiger |first1=Eduardo |last2=Taiz |first2=Lincoln |name-list-style=vanc |chapter=Ch. 7: Topic 7.8: Photosystem I |chapter-url=http://4e.plantphys.net/article.php?ch=3&id=73 |title=Plant Physiology |publisher=Sinauer Associates |location=Sunderland, MA |year=2006 |isbn=0-87893-856-7 |edition=4th }}{{Dead link|date=April 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> These pigment molecules transmit the [[Förster resonance energy transfer|resonance energy]] from photons when they become photoexcited. Antenna molecules can absorb all [[wavelength]]s of light within the [[visible spectrum]].<ref name="kent">{{cite web |title=The Photosynthetic Process |url=http://kentsimmons.uwinnipeg.ca/cm1504/lightreact.htm |url-status=dead |archive-url=https://web.archive.org/web/20090219143934/http://kentsimmons.uwinnipeg.ca/cm1504/lightreact.htm |archive-date=2009-02-19 }}</ref> The number of these pigment molecules varies from organism to organism. For instance, the [[cyanobacteria|cyanobacterium]] ''Synechococcus elongatus'' (''Thermosynechococcus elongatus'') has about 100 chlorophylls and 20 carotenoids, whereas [[spinach]] chloroplasts have around 200 chlorophylls and 50 carotenoids.<ref name="kent"/><ref name="Nelson_2006"/> Located within the antenna complex of PSI are molecules of chlorophyll called [[P700]] reaction centers. The energy passed around by antenna molecules is directed to the reaction center. There may be as many as 120 or as few as 25 chlorophyll molecules per P700.<ref name="Shubin">{{cite journal | vauthors = Shubin VV, Karapetyan NV, Krasnovsky AA | title = Molecular arrangement of pigment-protein complex of photosystem 1 | journal = Photosynthesis Research | volume = 9 | issue = 1–2 | pages = 3–12 | date = January 1986 | pmid = 24442279 | doi = 10.1007/BF00029726 | bibcode = 1986PhoRe...9....3S | s2cid = 26158482 }}</ref>

=== P700 reaction center ===
{{main article|P700}}
The P700 reaction center is composed of modified [[Chlorophyll a|chlorophyll ''a'']] that best absorbs light at a wavelength of 700&nbsp;[[Nanometre|nm]].<ref name="rutherford">{{cite journal | vauthors = Rutherford AW, Heathcote P | title = Primary photochemistry in photosystem-I | journal = Photosynthesis Research | volume = 6 | issue = 4 | pages = 295–316 | date = December 1985 | pmid = 24442951 | doi = 10.1007/BF00054105 | bibcode = 1985PhoRe...6..295R | s2cid = 21845584 }}</ref> P700 receives energy from antenna molecules and uses the energy from each photon to raise an electron to a higher energy level (P700*). These electrons are moved in pairs in an [[redox|oxidation/reduction]] process from P700* to electron acceptors, leaving behind P700{{sup|+}}. The pair of P700* - P700{{sup|+}} has an [[electric potential]] of about −1.2 [[volt]]s. The reaction center is made of two chlorophyll molecules and is therefore referred to as a [[Dimer (chemistry)|dimer]].<ref name="Taiz"/> The dimer is thought to be composed of one chlorophyll ''a'' molecule and one chlorophyll ''a''′ molecule. However, if P700 forms a complex with other antenna molecules, it can no longer be a dimer.<ref name="Shubin"/>

=== Modified chlorophyll A{{sub|0}} and A{{sub|1}}  ===

The two modified chlorophyll molecules are early electron acceptors in PSI. They are present one per PsaA/PsaB side, forming two branches electrons can take to reach F{{sub|x}}. A{{sub|0}} accepts electrons from P700*, passes it to A{{sub|1}} of the same side, which then passes the electron to the quinone on the same side. Different species seems to have different preferences for either A/B branch.<ref name=Grotjohann>{{cite book |last1=Grotjohann |first1=I |last2=Fromme |first2=P |title=Encyclopedia of biological chemistry |location=London |isbn=978-0-12-378630-2 |edition=Second |chapter=Photosystem I|year=2013 |pages=503–507 |doi=10.1016/B978-0-12-378630-2.00287-5}}</ref>

=== Phylloquinone ===

A [[phylloquinone]], sometimes called vitamin K{{sub|1}},<ref name="itoh">{{cite journal|last1=Itoh|first1=Shigeru|last2=Iwaki|first2=Masayo|name-list-style=vanc|year=1989|title=Vitamin K{{sub|1}} (Phylloquinone) Restores the Turnover of FeS centers of Ether-extracted Spinach PSI Particles|journal=FEBS Letters|volume=243|issue=1|pages=47–52|doi=10.1016/0014-5793(89)81215-3|doi-access=free|s2cid=84602152}}</ref> is the next early electron acceptor in PSI. It oxidizes A{{sub|1}} in order to receive the electron and in turn is re-oxidized by F{{sub|x}}, from which the electron is passed to F{{sub|b}} and F{{sub|a}}.<ref name="itoh"/><ref>{{cite journal | vauthors = Palace GP, Franke JE, Warden JT | title = Is phylloquinone an obligate electron carrier in photosystem I? | journal = FEBS Letters | volume = 215 | issue = 1 | pages = 58–62 | date = May 1987 | pmid = 3552735 | doi = 10.1016/0014-5793(87)80113-8 | s2cid = 42983611 | doi-access = free | bibcode = 1987FEBSL.215...58P }}</ref> The reduction of F<sub>x</sub> appears to be the rate-limiting step.<ref name=Grotjohann/>

=== Iron–sulfur complex ===

Three proteinaceous [[Iron–sulfur cluster|iron–sulfur]] reaction centers are found in PSI. Labeled F{{sub|x}}, F{{sub|a}}, and F{{sub|b}}, they serve as electron relays.<ref name="Vassiliev"/> F{{sub|a}} and F{{sub|b}} are bound to [[protein subunit]]s of the PSI complex and F{{sub|x}} is tied to the PSI complex.<ref name="Vassiliev"/> Various experiments have shown some disparity between theories of iron–sulfur cofactor orientation and operation order.<ref name="Vassiliev">{{cite journal | vauthors = Vassiliev IR, Antonkine ML, Golbeck JH | title = Iron-sulfur clusters in type I reaction centers | journal = Biochimica et Biophysica Acta (BBA) - Bioenergetics | volume = 1507 | issue = 1–3 | pages = 139–60 | date = October 2001 | pmid = 11687212 | doi = 10.1016/S0005-2728(01)00197-9 | doi-access =  }}</ref> In one model, F{{sub|x}} passes an electron to F{{sub|a}}, which passes it on to F{{sub|b}} to reach the ferredoxin.<ref name=Grotjohann/>

=== Ferredoxin ===

[[Ferredoxin]] (Fd) is a [[solubility|soluble]] protein that facilitates reduction of {{chem|NADP|+}} to NADPH.<ref name="Forti">{{cite journal |doi=10.1016/0014-5793(85)80698-0 |last1=Forti |first1=Georgio |first2 = Paola |last2 = Maria |first3 = Giovanna |last3=Grubas | name-list-style = vanc |title=Two Sites of Interaction of Ferredoxin with thylakoids |journal=FEBS Letters |volume=186 |issue=2 |pages=149–152 |year=1985 |s2cid=83495051 |doi-access=free |bibcode=1985FEBSL.186..149F }}</ref> Fd moves to carry an electron either to a lone thylakoid or to an [[enzyme]] that reduces {{chem|NADP|+}}.<ref name="Forti"/> Thylakoid membranes have one binding site for each function of Fd.<ref name="Forti"/> The main function of Fd is to carry an electron from the iron-sulfur complex to the enzyme [[ferredoxin-NADP+ reductase|ferredoxin–{{chem|NADP|+}} reductase]].<ref name="Forti"/>

=== Ferredoxin–{{chem|NADP|+}} reductase (FNR) ===

This enzyme transfers the electron from reduced ferredoxin to {{chem|NADP|+}} to complete the reduction to NADPH.<ref name="Madoz">{{cite journal | vauthors = Madoz J, Fernández Recio J, Gómez Moreno C, Fernández VM | title = Investigation of the Diaphorase Reaction of Ferredoxin–{{chem|NADP|+}} Reductase by Electrochemical Methods | journal = Bioelectrochemistry and Bioenergetics |volume=47 |issue=1 |pages=179–183 |date=November 1998 |doi=10.1016/S0302-4598(98)00175-5  | url = http://www.unizar.es/departamentos/bioquimica_biologia/investigacion/mmedina/Madoz1998.pdf }}</ref> [[Ferredoxin-NADP+ reductase|FNR]] may also accept an electron from NADPH by binding to it.<ref name="Madoz"/>

=== Plastocyanin ===
[[Plastocyanin]] is an electron carrier that transfers the electron from cytochrome b6f to the P700 cofactor of PSI in its ionized state P700{{sup|+}}.<ref name = "Raven">{{cite book |last1=Raven |first1=Peter H. |last2=Evert |first2=Ray F. |last3=Eichhorn |first3=Susan E. | name-list-style = vanc | chapter=Photosynthesis, Light, and Life |title=Biology of Plants |url=https://archive.org/details/biologyofplants00rave_0 |url-access=registration |publisher=W. H. Freeman |location=New York |year=2005 |pages=[https://archive.org/details/biologyofplants00rave_0/page/121 121–127] |edition=7th |isbn=978-0-7167-1007-3}}</ref><ref>{{cite journal | vauthors = Hope AB | title = Electron transfers amongst cytochrome f, plastocyanin and photosystem I: kinetics and mechanisms | journal = Biochimica et Biophysica Acta (BBA) - Bioenergetics | volume = 1456 | issue = 1 | pages = 5–26 | date = January 2000 | pmid = 10611452 | doi = 10.1016/S0005-2728(99)00101-2 | doi-access =  }}</ref>

== Ycf4 protein domain ==
The [[Ycf4 protein domain]] found on the thylakoid membrane is vital to photosystem&nbsp;I. This thylakoid transmembrane protein helps assemble the components of photosystem&nbsp;I. Without it, photosynthesis would be inefficient.<ref name="pmid9321389">{{cite journal | vauthors = Boudreau E, Takahashi Y, Lemieux C, Turmel M, Rochaix JD | title = The chloroplast ycf3 and ycf4 open reading frames of Chlamydomonas reinhardtii are required for the accumulation of the photosystem I complex | journal = The EMBO Journal | volume = 16 | issue = 20 | pages = 6095–104 | date = October 1997 | pmid = 9321389 | pmc = 1326293 | doi = 10.1093/emboj/16.20.6095 }}</ref>

== Evolution ==

Molecular data show that PSI likely evolved from the photosystems of [[green sulfur bacteria]]. The photosystems of green sulfur bacteria and those of [[cyanobacteria]], [[alga]]e, and higher plants are not the same, but there are many analogous functions and similar structures. Three main features are similar between the different photosystems.<ref name="Lockau">{{cite journal |doi=10.1111/j.1399-3054.1993.tb05512.x |last1=Lockau |first1=Wolfgang |first2 = Wolfgang|last2= Nitschke | name-list-style = vanc |title=Photosystem I and its Bacterial Counterparts |journal=Physiologia Plantarum |volume=88 |issue=2 |pages=372–381 |year=1993 |bibcode=1993PPlan..88..372L }}</ref> First, redox potential is negative enough to reduce ferredoxin.<ref name="Lockau"/> Next, the electron-accepting reaction centers include iron–sulfur proteins.<ref name="Lockau"/> Last, redox centres in complexes of both photosystems are constructed upon a protein subunit dimer.<ref name="Lockau"/> The photosystem of green sulfur bacteria even contains all of the same cofactors of the [[electron transport chain]] in PSI.<ref name="Lockau"/> The number and degree of similarities between the two photosystems strongly indicates that PSI and the analogous photosystem of green sulfur bacteria evolved from a common ancestral photosystem.

== See also ==
{{Portal|Biology}}
*[[Biohybrid solar cell]]

== References ==
{{reflist|32em}}

== External links ==
*[http://www.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb22_1.html Photosystem I: Molecule of the Month in the Protein Data Bank] {{Webarchive|url=https://web.archive.org/web/20110411021836/http://www.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb22_1.html |date=2011-04-11 }}
*[https://archive.today/20130221230635/http://4e.plantphys.net/article.php?ch=3&id=73 Photosystem I in A Companion to Plant Physiology]
*[http://www.bio.ic.ac.uk/research/barber/ James Barber FRS Photosystems I & II]

{{Other oxidoreductases}}
{{enzymes}}
{{Multienzyme complexes}}

[[Category:Photosynthesis]]
[[Category:Light reactions]]
[[Category:EC 1.97.1]]
[[Category:Protein complexes]]