ID   PSAB_PROHO              Reviewed;         661 AA.
AC   P58387; Q9AL92;
DT   16-NOV-2001, integrated into UniProtKB/Swiss-Prot.
DT   16-NOV-2001, sequence version 1.
DT   03-AUG-2022, entry version 89.
DE   RecName: Full=Photosystem I P700 chlorophyll a apoprotein A2;
DE            EC=1.97.1.12;
DE   AltName: Full=PsaB;
DE   Flags: Fragment;
GN   Name=psaB;
OS   Prochlorothrix hollandica.
OC   Bacteria; Cyanobacteria; Pseudanabaenales; Prochlorotrichaceae;
OC   Prochlorothrix.
OX   NCBI_TaxID=1223;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RA   Mychkine E., Bullerjahn G.S.;
RT   "Structural variability in the psaA/psaB proteins of Prochlorothrix.";
RL   Submitted (FEB-2001) to the EMBL/GenBank/DDBJ databases.
CC   -!- FUNCTION: PsaA and PsaB bind P700, the primary electron donor of
CC       photosystem I (PSI), as well as the electron acceptors A0, A1 and FX.
CC       PSI is a plastocyanin/cytochrome c6-ferredoxin oxidoreductase,
CC       converting photonic excitation into a charge separation, which
CC       transfers an electron from the donor P700 chlorophyll pair to the
CC       spectroscopically characterized acceptors A0, A1, FX, FA and FB in
CC       turn. Oxidized P700 is reduced on the lumenal side of the thylakoid
CC       membrane by plastocyanin or cytochrome c6 (By similarity).
CC       {ECO:0000250}.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=hnu + oxidized [2Fe-2S]-[ferredoxin] + reduced [plastocyanin]
CC         = oxidized [plastocyanin] + reduced [2Fe-2S]-[ferredoxin];
CC         Xref=Rhea:RHEA:30407, Rhea:RHEA-COMP:10000, Rhea:RHEA-COMP:10001,
CC         Rhea:RHEA-COMP:10039, Rhea:RHEA-COMP:10040, ChEBI:CHEBI:29036,
CC         ChEBI:CHEBI:30212, ChEBI:CHEBI:33737, ChEBI:CHEBI:33738,
CC         ChEBI:CHEBI:49552; EC=1.97.1.12;
CC   -!- COFACTOR:
CC       Note=PSI electron transfer chain: 5 chlorophyll a, 1 chlorophyll a', 2
CC       phylloquinones and 3 4Fe-4S clusters. PSI core antenna: 90 chlorophyll
CC       a, 22 carotenoids, 3 phospholipids and 1 galactolipid. P700 is a
CC       chlorophyll a/chlorophyll a' dimer, A0 is one or more chlorophyll a, A1
CC       is one or both phylloquinones and FX is a shared 4Fe-4S iron-sulfur
CC       center. {ECO:0000250};
CC   -!- SUBUNIT: The PsaA/B heterodimer binds the P700 chlorophyll special pair
CC       and subsequent electron acceptors. PSI consists of a core antenna
CC       complex that captures photons, and an electron transfer chain that
CC       converts photonic excitation into a charge separation. The
CC       cyanobacterial PSI reaction center is composed of one copy each of
CC       PsaA,B,C,D,E,F,I,J,K,L,M and X, and forms trimeric complexes (By
CC       similarity). {ECO:0000250}.
CC   -!- SUBCELLULAR LOCATION: Cellular thylakoid membrane {ECO:0000250}; Multi-
CC       pass membrane protein {ECO:0000250}.
CC   -!- SIMILARITY: Belongs to the PsaA/PsaB family. {ECO:0000305}.
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DR   EMBL; AY026898; AAK08971.1; -; Genomic_DNA.
DR   AlphaFoldDB; P58387; -.
DR   SMR; P58387; -.
DR   GO; GO:0016021; C:integral component of membrane; IEA:UniProtKB-KW.
DR   GO; GO:0009522; C:photosystem I; IEA:UniProtKB-KW.
DR   GO; GO:0031676; C:plasma membrane-derived thylakoid membrane; IEA:UniProtKB-SubCell.
DR   GO; GO:0051539; F:4 iron, 4 sulfur cluster binding; IEA:UniProtKB-KW.
DR   GO; GO:0016168; F:chlorophyll binding; IEA:UniProtKB-KW.
DR   GO; GO:0046872; F:metal ion binding; IEA:UniProtKB-KW.
DR   GO; GO:0016491; F:oxidoreductase activity; IEA:UniProtKB-KW.
DR   GO; GO:0015979; P:photosynthesis; IEA:UniProtKB-KW.
DR   Gene3D; 1.20.1130.10; -; 1.
DR   InterPro; IPR001280; PSI_PsaA/B.
DR   InterPro; IPR020586; PSI_PsaA/B_CS.
DR   InterPro; IPR036408; PSI_PsaA/B_sf.
DR   InterPro; IPR006244; PSI_PsaB.
DR   Pfam; PF00223; PsaA_PsaB; 1.
DR   PRINTS; PR00257; PHOTSYSPSAAB.
DR   SUPFAM; SSF81558; SSF81558; 1.
DR   TIGRFAMs; TIGR01336; psaB; 1.
DR   PROSITE; PS00419; PHOTOSYSTEM_I_PSAAB; 1.
PE   3: Inferred from homology;
KW   4Fe-4S; Chlorophyll; Chromophore; Electron transport; Iron; Iron-sulfur;
KW   Magnesium; Membrane; Metal-binding; Oxidoreductase; Photosynthesis;
KW   Photosystem I; Thylakoid; Transmembrane; Transmembrane helix; Transport.
FT   CHAIN           1..>661
FT                   /note="Photosystem I P700 chlorophyll a apoprotein A2"
FT                   /id="PRO_0000088646"
FT   TRANSMEM        46..69
FT                   /note="Helical; Name=I"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        135..158
FT                   /note="Helical; Name=II"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        175..199
FT                   /note="Helical; Name=III"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        273..291
FT                   /note="Helical; Name=IV"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        335..358
FT                   /note="Helical; Name=V"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        374..400
FT                   /note="Helical; Name=VI"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        422..443
FT                   /note="Helical; Name=VII"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        522..540
FT                   /note="Helical; Name=VIII"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        580..601
FT                   /note="Helical; Name=IX"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        648..>661
FT                   /note="Helical; Name=X"
FT                   /evidence="ECO:0000255"
FT   BINDING         564
FT                   /ligand="[4Fe-4S] cluster"
FT                   /ligand_id="ChEBI:CHEBI:49883"
FT                   /ligand_note="ligand shared between dimeric partners"
FT                   /evidence="ECO:0000250"
FT   BINDING         573
FT                   /ligand="[4Fe-4S] cluster"
FT                   /ligand_id="ChEBI:CHEBI:49883"
FT                   /ligand_note="ligand shared between dimeric partners"
FT                   /evidence="ECO:0000250"
FT   BINDING         659
FT                   /ligand="chlorophyll a"
FT                   /ligand_id="ChEBI:CHEBI:58416"
FT                   /ligand_label="B1"
FT                   /ligand_part="Mg"
FT                   /ligand_part_id="ChEBI:CHEBI:25107"
FT                   /note="axial binding residue"
FT                   /evidence="ECO:0000250"
FT   NON_TER         661
SQ   SEQUENCE   661 AA;  73328 MW;  CC03FCDC126712C7 CRC64;
     MATKFPKFSQ DLAQDPTTRR IWYGIATAHD FEMHDGMTEE NLYQKIFASH FGHLAIIFLW
     TSGNLFHVAW QGNFAQWVAD PLNTRPIAHA IWDPHFGEAA IEAFTQSDAS CAVNIAYSGV
     YHWWYTIGMR TAADLYQGSI FLMVLAALML FAGWLHLQPK FRPSLAWFKN AESRLNHHLA
     GLFGVSSLAW AGHLIHVAIP ASRGETVNWG NFMSTPPHPA GLAPFFSGNW SVYAANPDTT
     GHVFNTSEGA GTAILTFLGG FHPQTQAMWL TDIAHHHLAI AVIFIIAGHM YKTNFGIGHS
     MKEILKTHRS PEGTPFGGML GAGHDGLYDT INNSLHFQLG LALAALGVVT SLVAQHMYSM
     PSYAFIAQDF TTQAALYVHH QYIAIFLMCG AFAHGAIFFV RDYDHEANKN NVLGRVLEHK
     EAIISHLSWV SLFLGFHTLA LVHNDVVVAF ATPEKQILLE PVFAQFVQAA SGKALYGFNV
     LLVNPDSAAS IASDYIAGPH FWLDAINSGV NSLFLTIGPG DFLVHHAIAL GLHTTTLILV
     KGALDARGSK LMPDKKDFGY SFPCDGPGRG GTCDISAWDS FYLAVFWALN TAGWLTFYWH
     WKHLSIWQDN VAQFNESSTY LMGWFRDYLW LNSAQLINGY NPFGSQQLAV WAWMFLFGHL
     V