ID   PSAB_PROM3              Reviewed;         749 AA.
AC   A2CC72;
DT   11-SEP-2007, integrated into UniProtKB/Swiss-Prot.
DT   20-FEB-2007, sequence version 1.
DT   27-MAR-2024, entry version 96.
DE   RecName: Full=Photosystem I P700 chlorophyll a apoprotein A2 {ECO:0000255|HAMAP-Rule:MF_00482};
DE            EC=1.97.1.12 {ECO:0000255|HAMAP-Rule:MF_00482};
DE   AltName: Full=PsaB {ECO:0000255|HAMAP-Rule:MF_00482};
GN   Name=psaB {ECO:0000255|HAMAP-Rule:MF_00482};
GN   OrderedLocusNames=P9303_23471;
OS   Prochlorococcus marinus (strain MIT 9303).
OC   Bacteria; Cyanobacteriota; Cyanophyceae; Synechococcales;
OC   Prochlorococcaceae; Prochlorococcus.
OX   NCBI_TaxID=59922;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
RC   STRAIN=MIT 9303;
RX   PubMed=18159947; DOI=10.1371/journal.pgen.0030231;
RA   Kettler G.C., Martiny A.C., Huang K., Zucker J., Coleman M.L., Rodrigue S.,
RA   Chen F., Lapidus A., Ferriera S., Johnson J., Steglich C., Church G.M.,
RA   Richardson P., Chisholm S.W.;
RT   "Patterns and implications of gene gain and loss in the evolution of
RT   Prochlorococcus.";
RL   PLoS Genet. 3:2515-2528(2007).
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. {ECO:0000255|HAMAP-
CC       Rule:MF_00482}.
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; Evidence={ECO:0000255|HAMAP-
CC         Rule:MF_00482};
CC   -!- COFACTOR:
CC       Note=PSI electron transfer chain: 5 divinyl chlorophyll a, 1 divinyl
CC       chlorophyll a', 2 phylloquinones and 3 4Fe-4S clusters. PSI core
CC       antenna: 90 divinyl chlorophyll a, 22 carotenoids, 3 phospholipids and
CC       1 galactolipid. P700 is a divinyl chlorophyll a/divinyl chlorophyll a'
CC       dimer, A0 is one or more divinyl chlorophyll a, A1 is one or both
CC       phylloquinones and FX is a shared 4Fe-4S iron-sulfur center.
CC       {ECO:0000255|HAMAP-Rule:MF_00482};
CC   -!- SUBUNIT: The PsaA/B heterodimer binds the P700 divinyl chlorophyll
CC       special pair and subsequent electron acceptors. PSI consists of a core
CC       antenna complex that captures photons, and an electron transfer chain
CC       that 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.
CC       {ECO:0000255|HAMAP-Rule:MF_00482}.
CC   -!- SUBCELLULAR LOCATION: Cellular thylakoid membrane {ECO:0000255|HAMAP-
CC       Rule:MF_00482}; Multi-pass membrane protein {ECO:0000255|HAMAP-
CC       Rule:MF_00482}.
CC   -!- SIMILARITY: Belongs to the PsaA/PsaB family. {ECO:0000255|HAMAP-
CC       Rule:MF_00482}.
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DR   EMBL; CP000554; ABM79082.1; -; Genomic_DNA.
DR   RefSeq; WP_011826945.1; NC_008820.1.
DR   AlphaFoldDB; A2CC72; -.
DR   SMR; A2CC72; -.
DR   STRING; 59922.P9303_23471; -.
DR   KEGG; pmf:P9303_23471; -.
DR   HOGENOM; CLU_016126_1_0_3; -.
DR   BioCyc; PMAR59922:G1G80-2064-MONOMER; -.
DR   Proteomes; UP000002274; Chromosome.
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:0009055; F:electron transfer activity; IEA:UniProtKB-UniRule.
DR   GO; GO:0000287; F:magnesium ion binding; IEA:UniProtKB-UniRule.
DR   GO; GO:0015979; P:photosynthesis; IEA:UniProtKB-UniRule.
DR   Gene3D; 1.20.1130.10; Photosystem I PsaA/PsaB; 1.
DR   HAMAP; MF_00482; PSI_PsaB; 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   NCBIfam; TIGR01336; psaB; 1.
DR   PANTHER; PTHR30128; OUTER MEMBRANE PROTEIN, OMPA-RELATED; 1.
DR   PANTHER; PTHR30128:SF75; PHOTOSYSTEM I P700 CHLOROPHYLL A APOPROTEIN A2; 1.
DR   Pfam; PF00223; PsaA_PsaB; 1.
DR   PIRSF; PIRSF002905; PSI_A; 1.
DR   PRINTS; PR00257; PHOTSYSPSAAB.
DR   SUPFAM; SSF81558; Photosystem I subunits PsaA/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..749
FT                   /note="Photosystem I P700 chlorophyll a apoprotein A2"
FT                   /id="PRO_0000300018"
FT   TRANSMEM        46..69
FT                   /note="Helical; Name=I"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   TRANSMEM        135..158
FT                   /note="Helical; Name=II"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   TRANSMEM        175..199
FT                   /note="Helical; Name=III"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   TRANSMEM        273..291
FT                   /note="Helical; Name=IV"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   TRANSMEM        343..366
FT                   /note="Helical; Name=V"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   TRANSMEM        382..408
FT                   /note="Helical; Name=VI"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   TRANSMEM        430..452
FT                   /note="Helical; Name=VII"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   TRANSMEM        532..550
FT                   /note="Helical; Name=VIII"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   TRANSMEM        590..611
FT                   /note="Helical; Name=IX"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   TRANSMEM        658..680
FT                   /note="Helical; Name=X"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   TRANSMEM        722..742
FT                   /note="Helical; Name=XI"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   BINDING         574
FT                   /ligand="[4Fe-4S] cluster"
FT                   /ligand_id="ChEBI:CHEBI:49883"
FT                   /ligand_note="ligand shared between dimeric partners"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   BINDING         583
FT                   /ligand="[4Fe-4S] cluster"
FT                   /ligand_id="ChEBI:CHEBI:49883"
FT                   /ligand_note="ligand shared between dimeric partners"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   BINDING         669
FT                   /ligand="divinyl chlorophyll a"
FT                   /ligand_id="ChEBI:CHEBI:73095"
FT                   /ligand_label="B1"
FT                   /ligand_part="Mg"
FT                   /ligand_part_id="ChEBI:CHEBI:25107"
FT                   /note="axial binding residue"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   BINDING         677
FT                   /ligand="divinyl chlorophyll a"
FT                   /ligand_id="ChEBI:CHEBI:73095"
FT                   /ligand_label="B3"
FT                   /ligand_part="Mg"
FT                   /ligand_part_id="ChEBI:CHEBI:25107"
FT                   /note="axial binding residue"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   BINDING         685
FT                   /ligand="divinyl chlorophyll a"
FT                   /ligand_id="ChEBI:CHEBI:73095"
FT                   /ligand_label="B3"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
FT   BINDING         686
FT                   /ligand="phylloquinone"
FT                   /ligand_id="ChEBI:CHEBI:18067"
FT                   /ligand_label="B"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00482"
SQ   SEQUENCE   749 AA;  83151 MW;  6C0AE61033501E0C CRC64;
     MATKFPSFSQ GLAQDPTTRR IWYGIATAHD FESHDGMTEE RLYQKLFSTH FGHLAVIGLW
     VAGNLFHIAW QGNFEQWVAD PQNVQPIAHA IWDPHFGQGI SDALTQAGAS RPVNICYSGL
     YHWWYTIGMR TNTELYQGAI FIDILVAWLL FGGWLHLQPK FRPSLAWFKN AEAMMNHHLA
     VLFGFTNIAW TGHLVHVAIP ESRGQHVGWD NFLTVLPHPE GLTPFFTGNW GAYAQNPDSL
     NHAFGTSEGA GTAILTFLGG VHPQSGALWL TDISHHHIAI GVFMIIGGHM YRNSFGIGHT
     FKEITDGHNT SHPNDPHKDG FREKIGHYGL SHTGITDTIN NSLHFQLGLA LACLGTAASL
     VAHHMGALPS YAFIAQDYTT QAALYTHHQY IAIFLMCGAF SHGAIFFVRD YDPEANKDNV
     LARVLETKEA LISHLSWVCM LLGFHTLALY LHNDVVIAFG TPEKQILVEP IFAQFIQAAS
     GKVMYGLDVL LANANSAPSL AAAGMPGDHY WMDLINASPE VSNFMPIGPG DFLVHHGIAL
     GLHTTALILI KGALDARGSK LMPDKKDFGY AFACDGPGRG GTCDISAWDS TYMAIFWALN
     TIAWATYYWH WKHLAAWQGN MAQFNESSTH LMGWFRDYLW INSSQIINGY NPFGINNLSP
     WAYMFLAGHL VWATGFMFLI SWRGYWQELI ETLVWAHQRS PIANLVGWRD KPVALSIVQA
     RLVGVTHFAV GNIFTFGAFV IASTASKFG
//