HAMAP

Accession	MF_00482
Dates	1-JUN-2001 (Created) 10-OCT-2011 (Last updated, Version 55)

Data class

Protein

Predictors

HAMAP; MF_00482; [distribution of match scores in UniProtKB];[seed alignment for MF_00482]

Names

PSI_PsaB

Identifier

PSAB

Protein name

RecName: Full=Photosystem I P700 chlorophyll a apoprotein A2; EC=1.97.1.12; AltName: Full=PsaB;

Protein name

RecName: Full=Photosystem I P700 chlorophyll a apoprotein A2; EC=1.97.1.12; AltName: Full=PSI-B; AltName: Full=PsaB;

Gene name

psaB

FUNCTION: PsaA and psaB bind P700, the primary electron donor of photosystem I (PSI), as well as the electron acceptors A0, A1 and FX. PSI is a plastocyanin/cytochrome c6-ferredoxin oxidoreductase, converting photonic excitation into a charge separation, which transfers an electron from the donor P700 chlorophyll pair to the spectroscopically characterized acceptors A0, A1, FX, FA and FB in turn. Oxidized P700 is reduced on the lumenal side of the thylakoid membrane by plastocyanin or cytochrome c6 (By similarity).

FUNCTION: PsaA and psaB bind P700, the primary electron donor of photosystem I (PSI), as well as the electron acceptors A0, A1 and FX. PSI is a plastocyanin-ferredoxin oxidoreductase, converting photonic excitation into a charge separation, which transfers an electron from the donor P700 chlorophyll pair to the spectroscopically characterized acceptors A0, A1, FX, FA and FB in turn. Oxidized P700 is reduced on the lumenal side of the thylakoid membrane by plastocyanin (By similarity).

CATALYTIC ACTIVITY: Reduced plastocyanin + oxidized ferredoxin + light = oxidized plastocyanin + reduced ferredoxin.

COFACTOR: PSI electron transfer chain: 5 chlorophyll a, 1 chlorophyll a', 2 phylloquinones and 3 4Fe-4S clusters. PSI core antenna: 90 chlorophyll a, 22 carotenoids, 3 phospholipids and 1 galactolipid. P700 is a chlorophyll a/chlorophyll a' dimer, A0 is one or more chlorophyll a, A1 is one or both phylloquinones and FX is a shared 4Fe-4S iron-sulfur center (By similarity).

SUBUNIT: The psaA/B heterodimer binds the P700 chlorophyll special pair and subsequent electron acceptors. PSI consists of a core antenna complex that captures photons, and an electron transfer chain that converts photonic excitation into a charge separation. The cyanobacterial PSI reaction center is composed of one copy each of psaA,B,C,D,E,F,I,J,K,L,M and X, and forms trimeric complexes (By similarity).

COFACTOR: PSI electron transfer chain: 5 divinyl chlorophyll a, 1 divinyl chlorophyll a', 2 phylloquinones and 3 4Fe-4S clusters. PSI core antenna: 90 divinyl chlorophyll a, 22 carotenoids, 3 phospholipids and 1 galactolipid. P700 is a divinyl chlorophyll a/divinyl chlorophyll a' dimer, A0 is one or more divinyl chlorophyll a, A1 is one or both phylloquinones and FX is a shared 4Fe-4S iron-sulfur center (By similarity).

SUBUNIT: The psaA/B heterodimer binds the P700 divinyl chlorophyll special pair and subsequent electron acceptors. PSI consists of a core antenna complex that captures photons, and an electron transfer chain that converts photonic excitation into a charge separation. The cyanobacterial PSI reaction center is composed of one copy each of psaA,B,C,D,E,F,I,J,K,L,M and X, and forms trimeric complexes (By similarity).

COFACTOR: P700 is a chlorophyll a/chlorophyll a' dimer, A0 is one or more chlorophyll a, A1 is one or both phylloquinones and FX is a shared 4Fe-4S iron-sulfur center (By similarity).

SUBUNIT: The psaA/B heterodimer binds the P700 chlorophyll special pair and subsequent electron acceptors. PSI consists of a core antenna complex that captures photons, and an electron transfer chain that converts photonic excitation into a charge separation. The eukaryotic PSI reaction center is composed of at least 11 subunits (By similarity).

SUBCELLULAR LOCATION: Plastid, chloroplast thylakoid membrane; Multi-pass membrane protein (By similarity).

SUBCELLULAR LOCATION: Cell inner membrane; Multi-pass membrane protein (By similarity).

SUBCELLULAR LOCATION: Cellular thylakoid membrane; Multi-pass membrane protein (By similarity).

SIMILARITY: Belongs to the psaA/psaB family.

Pfam	PF00223; PsaA_PsaB; 1;
PIRSF	PIRSF002905; PSI_A; 1;
PRINTS	PR00257; PHOTSYSPSAAB; 1;
TIGRFAMs	TIGR01335; PsaA; 1;
PROSITE	PS00419; PHOTOSYSTEM_I_PSAAB; 1;

Transport, Electron transport, Photosynthesis.

Cell membrane, Cell inner membrane.

Thylakoid.

Photosystem I, Chromophore, Chlorophyll, Metal-binding, Iron, Oxidoreductase, Magnesium, Iron-sulfur, 4Fe-4S, Membrane, Transmembrane, Transmembrane helix.

GO:0009055; Molecular function: electron carrier activity.
GO:0000287; Molecular function: magnesium ion binding.
GO:0015979; Biological process: photosynthesis.
GO:0055114; Biological process: oxidation-reduction process.

GO:0009535; Cellular component: chloroplast thylakoid membrane.

GO:0005886; Cellular component: plasma membrane.

GO:0042651; Cellular component: thylakoid membrane.

From: PSAB_THEEB (P0A407)
Key		From		To		Description		Condition		FTGroup
TRANSMEM		39		70		Helical; Name=I (Potential)
TRANSMEM		132		156		Helical; Name=II (Potential)
TRANSMEM		173		195		Helical; Name=III (Potential)
TRANSMEM		270		287		Helical; Name=IV (Potential)
TRANSMEM		335		358		Helical; Name=V (Potential)
TRANSMEM		369		400		Helical; Name=VI (Potential)
TRANSMEM		420		449		Helical; Name=VII (Potential)
TRANSMEM		521		545		Helical; Name=VIII (Potential)
TRANSMEM		579		610		Helical; Name=IX (Potential)
TRANSMEM		651		672		Helical; Name=X (Potential)
TRANSMEM		709		737		Helical; Name=XI (Potential)
METAL		566		566		Iron-sulfur (4Fe-4S); shared with dimeric partner (By similarity)		C
METAL		575		575		Iron-sulfur (4Fe-4S); shared with dimeric partner (By similarity)		C

Key		From		To		Description		Condition		FTGroup
METAL		661		661		Magnesium (chlorophyll-a B1 axial ligand; P700 special pair) (By similarity)		H
METAL		669		669		Magnesium (chlorophyll-a B3 axial ligand) (By similarity)		M
BINDING		677		677		Chlorophyll-a B3 (By similarity)		Y

Key		From		To		Description		Condition		FTGroup
METAL		661		661		Magnesium (divinyl chlorophyll-a B1 axial ligand; P700 special pair) (By similarity)		H
METAL		669		669		Magnesium (divinyl chlorophyll-a B3 axial ligand) (By similarity)		M
BINDING		677		677		Divinyl chlorophyll-a B3 (By similarity)		Y

Key		From		To		Description		Condition		FTGroup
BINDING		678		678		Phylloquinone B (By similarity)		W

Size range:	644-776 amino acids
Related UniRules:	None
Template:	P09144 (PSAB_CHLRE); P06512 (PSAB_SPIOL); P0A407 (PSAB_THEEB); P0A408 (PSAB_SYNEN); P29255 (PSAB_SYNY3): [Recover all]
Scope:	Bacteria; Cyanobacteria Plastid
Fusion:	Nter: None; Cter: <OmpA-like domain>
Duplicate:	in NOSS1, ANAVT
Plasmid encoded:	None
Comments:	G.violaceus is fused to an OmpA-like domain. AMPCA is atypical.