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Entry version 58 (16 Jan 2019)
Sequence version 1 (17 Oct 2006)
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Photosystem I iron-sulfur center



Citrus sinensis (Sweet orange) (Citrus aurantium var. sinensis)
Reviewed-Annotation score:

Annotation score:3 out of 5

<p>The annotation score provides a heuristic measure of the annotation content of a UniProtKB entry or proteome. This score <strong>cannot</strong> be used as a measure of the accuracy of the annotation as we cannot define the ‘correct annotation’ for any given protein.<p><a href='/help/annotation_score' target='_top'>More...</a></p>
-Protein inferred from homologyi <p>This indicates the type of evidence that supports the existence of the protein. Note that the ‘protein existence’ evidence does not give information on the accuracy or correctness of the sequence(s) displayed.<p><a href='/help/protein_existence' target='_top'>More...</a></p>

<p>This section provides any useful information about the protein, mostly biological knowledge.<p><a href='/help/function_section' target='_top'>More...</a></p>Functioni

Apoprotein for the two 4Fe-4S centers FA and FB of photosystem I (PSI); essential for photochemical activity. FB is the terminal electron acceptor of PSI, donating electrons to ferredoxin. The C-terminus interacts with PsaA/B/D and helps assemble the protein into the PSI complex. Required for binding of PsaD and PsaE to PSI. 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.UniRule annotation

<p>This subsection of the <a href="">Function</a> section describes the catalytic activity of an enzyme, i.e. a chemical reaction that the enzyme catalyzes.<p><a href='/help/catalytic_activity' target='_top'>More...</a></p>Catalytic activityi

<p>This subsection of the ‘Function’ section provides information relevant to cofactors. A cofactor is any non-protein substance required for a protein to be catalytically active. Some cofactors are inorganic, such as the metal atoms zinc, iron, and copper in various oxidation states. Others, such as most vitamins, are organic.<p><a href='/help/cofactor' target='_top'>More...</a></p>Cofactori

[4Fe-4S] clusterUniRule annotationNote: Binds 2 [4Fe-4S] clusters. Cluster 2 is most probably the spectroscopically characterized electron acceptor FA and cluster 1 is most probably FB.UniRule annotation


Feature keyPosition(s)DescriptionActionsGraphical viewLength
<p>This subsection of the ‘Function’ section indicates at which position the protein binds a given metal ion. The nature of the metal is indicated in the ‘Description’ field.<p><a href='/help/metal' target='_top'>More...</a></p>Metal bindingi11Iron-sulfur 1 (4Fe-4S)UniRule annotation1
Metal bindingi14Iron-sulfur 1 (4Fe-4S)UniRule annotation1
Metal bindingi17Iron-sulfur 1 (4Fe-4S)UniRule annotation1
Metal bindingi21Iron-sulfur 2 (4Fe-4S)UniRule annotation1
Metal bindingi48Iron-sulfur 2 (4Fe-4S)UniRule annotation1
Metal bindingi51Iron-sulfur 2 (4Fe-4S)UniRule annotation1
Metal bindingi54Iron-sulfur 2 (4Fe-4S)UniRule annotation1
Metal bindingi58Iron-sulfur 1 (4Fe-4S)UniRule annotation1

<p>The <a href="">Gene Ontology (GO)</a> project provides a set of hierarchical controlled vocabulary split into 3 categories:<p><a href='/help/gene_ontology' target='_top'>More...</a></p>GO - Molecular functioni

GO - Biological processi

<p>UniProtKB Keywords constitute a <a href="">controlled vocabulary</a> with a hierarchical structure. Keywords summarise the content of a UniProtKB entry and facilitate the search for proteins of interest.<p><a href='/help/keywords' target='_top'>More...</a></p>Keywordsi

Molecular functionOxidoreductase
Biological processElectron transport, Photosynthesis, Transport
Ligand4Fe-4S, Iron, Iron-sulfur, Metal-binding

<p>This section provides information about the protein and gene name(s) and synonym(s) and about the organism that is the source of the protein sequence.<p><a href='/help/names_and_taxonomy_section' target='_top'>More...</a></p>Names & Taxonomyi

<p>This subsection of the <a href="">Names and taxonomy</a> section provides an exhaustive list of all names of the protein, from commonly used to obsolete, to allow unambiguous identification of a protein.<p><a href='/help/protein_names' target='_top'>More...</a></p>Protein namesi
Recommended name:
Photosystem I iron-sulfur centerUniRule annotation (EC: annotation)
Alternative name(s):
9 kDa polypeptideUniRule annotation
PSI-CUniRule annotation
Photosystem I subunit VIIUniRule annotation
PsaCUniRule annotation
<p>This subsection of the <a href="">Names and taxonomy</a> section indicates the name(s) of the gene(s) that code for the protein sequence(s) described in the entry. Four distinct tokens exist: ‘Name’, ‘Synonyms’, ‘Ordered locus names’ and ‘ORF names’.<p><a href='/help/gene_name' target='_top'>More...</a></p>Gene namesi
Name:psaCUniRule annotation
<p>This subsection of the <a href="">Names and taxonomy</a> section indicates if the gene coding for the protein originates from the hydrogenosome, the mitochondrion, the nucleomorph, different plastids or a plasmid. The absence of this section means that the gene is located in one of the main chromosomal element(s).<p><a href='/help/encoded_on' target='_top'>More...</a></p>Encoded oniPlastid; Chloroplast
<p>This subsection of the <a href="">Names and taxonomy</a> section provides information on the name(s) of the organism that is the source of the protein sequence.<p><a href='/help/organism-name' target='_top'>More...</a></p>OrganismiCitrus sinensis (Sweet orange) (Citrus aurantium var. sinensis)
<p>This subsection of the <a href="">Names and taxonomy</a> section shows the unique identifier assigned by the NCBI to the source organism of the protein. This is known as the ‘taxonomic identifier’ or ‘taxid’.<p><a href='/help/taxonomic_identifier' target='_top'>More...</a></p>Taxonomic identifieri2711 [NCBI]
<p>This subsection of the <a href="">Names and taxonomy</a> section contains the taxonomic hierarchical classification lineage of the source organism. It lists the nodes as they appear top-down in the taxonomic tree, with the more general grouping listed first.<p><a href='/help/taxonomic_lineage' target='_top'>More...</a></p>Taxonomic lineageiEukaryotaViridiplantaeStreptophytaEmbryophytaTracheophytaSpermatophytaMagnoliophytaeudicotyledonsGunneridaePentapetalaerosidsmalvidsSapindalesRutaceaeAurantioideaeCitrus

<p>This section provides information on the location and the topology of the mature protein in the cell.<p><a href='/help/subcellular_location_section' target='_top'>More...</a></p>Subcellular locationi

Extracellular region or secreted Cytosol Plasma membrane Cell wall Cytoskeleton Vacuole Chloroplast Endosome Peroxisome ER Golgi apparatus Nucleus Mitochondrion Manual annotation Automatic computational assertion Graphics by Christian Stolte & Seán O’Donoghue; Source: COMPARTMENTS

Keywords - Cellular componenti

Chloroplast, Membrane, Photosystem I, Plastid, Thylakoid

<p>This section describes post-translational modifications (PTMs) and/or processing events.<p><a href='/help/ptm_processing_section' target='_top'>More...</a></p>PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
<p>This subsection of the <a href="">PTM / Processing</a> section indicates that the initiator methionine is cleaved from the mature protein.<p><a href='/help/init_met' target='_top'>More...</a></p>Initiator methionineiRemovedBy similarity
<p>This subsection of the ‘PTM / Processing’ section describes the extent of a polypeptide chain in the mature protein following processing.<p><a href='/help/chain' target='_top'>More...</a></p>ChainiPRO_00002759762 – 81Photosystem I iron-sulfur centerAdd BLAST80

<p>This section provides information on the quaternary structure of a protein and on interaction(s) with other proteins or protein complexes.<p><a href='/help/interaction_section' target='_top'>More...</a></p>Interactioni

<p>This subsection of the <a href="">'Interaction'</a> section provides information about the protein quaternary structure and interaction(s) with other proteins or protein complexes (with the exception of physiological receptor-ligand interactions which are annotated in the <a href="">'Function'</a> section).<p><a href='/help/subunit_structure' target='_top'>More...</a></p>Subunit structurei

The eukaryotic PSI reaction center is composed of at least 11 subunits.UniRule annotation

<p>This section provides information on the tertiary and secondary structure of a protein.<p><a href='/help/structure_section' target='_top'>More...</a></p>Structurei

3D structure databases

Protein Model Portal of the PSI-Nature Structural Biology Knowledgebase


SWISS-MODEL Repository - a database of annotated 3D protein structure models


Database of comparative protein structure models


MobiDB: a database of protein disorder and mobility annotations


<p>This section provides information on sequence similarities with other proteins and the domain(s) present in a protein.<p><a href='/help/family_and_domains_section' target='_top'>More...</a></p>Family & Domainsi

Domains and Repeats

Feature keyPosition(s)DescriptionActionsGraphical viewLength
<p>This subsection of the <a href="">Family and Domains</a> section describes the position and type of a domain, which is defined as a specific combination of secondary structures organized into a characteristic three-dimensional structure or fold.<p><a href='/help/domain' target='_top'>More...</a></p>Domaini2 – 314Fe-4S ferredoxin-type 1UniRule annotationAdd BLAST30
Domaini39 – 684Fe-4S ferredoxin-type 2UniRule annotationAdd BLAST30

Keywords - Domaini


Phylogenomic databases

KEGG Orthology (KO)


Database of Orthologous Groups


Family and domain databases

HAMAP database of protein families

MF_01303 PSI_PsaC, 1 hit

Integrated resource of protein families, domains and functional sites

View protein in InterPro
IPR017896 4Fe4S_Fe-S-bd
IPR017900 4Fe4S_Fe_S_CS
IPR017491 PSI_PsaC

TIGRFAMs; a protein family database

TIGR03048 PS_I_psaC, 1 hit

PROSITE; a protein domain and family database

View protein in PROSITE
PS00198 4FE4S_FER_1, 2 hits
PS51379 4FE4S_FER_2, 2 hits

<p>This section displays by default the canonical protein sequence and upon request all isoforms described in the entry. It also includes information pertinent to the sequence(s), including <a href="">length</a> and <a href="">molecular weight</a>.<p><a href='/help/sequences_section' target='_top'>More...</a></p>Sequencei

<p>This subsection of the <a href="">Sequence</a> section indicates if the <a href="">canonical sequence</a> displayed by default in the entry is complete or not.<p><a href='/help/sequence_status' target='_top'>More...</a></p>Sequence statusi: Complete.

<p>This subsection of the <a href="">Sequence</a> section indicates if the <a href="">canonical sequence</a> displayed by default in the entry is in its mature form or if it represents the precursor.<p><a href='/help/sequence_processing' target='_top'>More...</a></p>Sequence processingi: The displayed sequence is further processed into a mature form.

Q09MC5-1 [UniParc]FASTAAdd to basket
« Hide
        10         20         30         40         50
60 70 80
Mass (Da):9,038
Last modified:October 17, 2006 - v1
<p>The checksum is a form of redundancy check that is calculated from the sequence. It is useful for tracking sequence updates.</p> <p>It should be noted that while, in theory, two different sequences could have the same checksum value, the likelihood that this would happen is extremely low.</p> <p>However UniProtKB may contain entries with identical sequences in case of multiple genes (paralogs).</p> <p>The checksum is computed as the sequence 64-bit Cyclic Redundancy Check value (CRC64) using the generator polynomial: x<sup>64</sup> + x<sup>4</sup> + x<sup>3</sup> + x + 1. The algorithm is described in the ISO 3309 standard. </p> <p class="publication">Press W.H., Flannery B.P., Teukolsky S.A. and Vetterling W.T.<br /> <strong>Cyclic redundancy and other checksums</strong><br /> <a href="">Numerical recipes in C 2nd ed., pp896-902, Cambridge University Press (1993)</a>)</p> Checksum:i68071DB57FC603BF

Sequence databases

Select the link destinations:

EMBL nucleotide sequence database


GenBank nucleotide sequence database


DNA Data Bank of Japan; a nucleotide sequence database

Links Updated
DQ864733 Genomic DNA Translation: ABI49072.1

NCBI Reference Sequences

YP_740528.1, NC_008334.1

Genome annotation databases

Database of genes from NCBI RefSeq genomes


KEGG: Kyoto Encyclopedia of Genes and Genomes


<p>This section is used to point to information related to entries and found in data collections other than UniProtKB.<p><a href='/help/cross_references_section' target='_top'>More...</a></p>Cross-referencesi

Sequence databases

Select the link destinations:
Links Updated
DQ864733 Genomic DNA Translation: ABI49072.1
RefSeqiYP_740528.1, NC_008334.1

3D structure databases


Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases


Phylogenomic databases


Family and domain databases

HAMAPiMF_01303 PSI_PsaC, 1 hit
InterProiView protein in InterPro
IPR017896 4Fe4S_Fe-S-bd
IPR017900 4Fe4S_Fe_S_CS
IPR017491 PSI_PsaC
TIGRFAMsiTIGR03048 PS_I_psaC, 1 hit
PROSITEiView protein in PROSITE
PS00198 4FE4S_FER_1, 2 hits
PS51379 4FE4S_FER_2, 2 hits

ProtoNet; Automatic hierarchical classification of proteins


<p>This section provides general information on the entry.<p><a href='/help/entry_information_section' target='_top'>More...</a></p>Entry informationi

<p>This subsection of the ‘Entry information’ section provides a mnemonic identifier for a UniProtKB entry, but it is not a stable identifier. Each reviewed entry is assigned a unique entry name upon integration into UniProtKB/Swiss-Prot.<p><a href='/help/entry_name' target='_top'>More...</a></p>Entry nameiPSAC_CITSI
<p>This subsection of the ‘Entry information’ section provides one or more accession number(s). These are stable identifiers and should be used to cite UniProtKB entries. Upon integration into UniProtKB, each entry is assigned a unique accession number, which is called ‘Primary (citable) accession number’.<p><a href='/help/accession_numbers' target='_top'>More...</a></p>AccessioniPrimary (citable) accession number: Q09MC5
<p>This subsection of the ‘Entry information’ section shows the date of integration of the entry into UniProtKB, the date of the last sequence update and the date of the last annotation modification (‘Last modified’). The version number for both the entry and the <a href="">canonical sequence</a> are also displayed.<p><a href='/help/entry_history' target='_top'>More...</a></p>Entry historyiIntegrated into UniProtKB/Swiss-Prot: February 6, 2007
Last sequence update: October 17, 2006
Last modified: January 16, 2019
This is version 58 of the entry and version 1 of the sequence. See complete history.
<p>This subsection of the ‘Entry information’ section indicates whether the entry has been manually annotated and reviewed by UniProtKB curators or not, in other words, if the entry belongs to the Swiss-Prot section of UniProtKB (<strong>reviewed</strong>) or to the computer-annotated TrEMBL section (<strong>unreviewed</strong>).<p><a href='/help/entry_status' target='_top'>More...</a></p>Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programPlant Protein Annotation Program
UniProt is an ELIXIR core data resource
Main funding by: National Institutes of Health

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