ID   CYB5S_TOBAC             Reviewed;         135 AA.
AC   P49099;
DT   01-FEB-1996, integrated into UniProtKB/Swiss-Prot.
DT   01-FEB-1996, sequence version 1.
DT   03-AUG-2022, entry version 104.
DE   RecName: Full=Cytochrome b5, seed isoform;
OS   Nicotiana tabacum (Common tobacco).
OC   Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta;
OC   Spermatophyta; Magnoliopsida; eudicotyledons; Gunneridae; Pentapetalae;
OC   asterids; lamiids; Solanales; Solanaceae; Nicotianoideae; Nicotianeae;
OC   Nicotiana.
OX   NCBI_TaxID=4097;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA].
RC   STRAIN=cv. Samsun; TISSUE=Seed;
RX   PubMed=7580860; DOI=10.1007/bf00239957;
RA   Napier J.A., Smith M.A., Stobart A.K., Shewry P.R.;
RT   "Isolation of a cDNA encoding a cytochrome b5 specifically expressed in
RT   developing tobacco seeds.";
RL   Planta 197:200-202(1995).
CC   -!- FUNCTION: Cytochrome b5 is a membrane bound hemoprotein which function
CC       as an electron carrier for several membrane bound oxygenases. May play
CC       a key role in the modification by desaturation of fatty acids in the
CC       endoplasmic reticulum, which in the developing seed is utilized for
CC       membrane synthesis and in the developmentally regulated production of
CC       large amounts of storage lipids.
CC   -!- SUBCELLULAR LOCATION: Endoplasmic reticulum membrane {ECO:0000250};
CC       Single-pass membrane protein {ECO:0000250}; Cytoplasmic side
CC       {ECO:0000250}. Microsome membrane {ECO:0000250}; Single-pass membrane
CC       protein {ECO:0000250}; Cytoplasmic side {ECO:0000250}.
CC   -!- TISSUE SPECIFICITY: Specifically expressed in developing seeds.
CC   -!- SIMILARITY: Belongs to the cytochrome b5 family. {ECO:0000305}.
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DR   EMBL; X80008; CAA56318.1; -; mRNA.
DR   PIR; S49200; S49200.
DR   RefSeq; XP_016493653.1; XM_016638167.1.
DR   AlphaFoldDB; P49099; -.
DR   SMR; P49099; -.
DR   STRING; 4097.P49099; -.
DR   GeneID; 107812972; -.
DR   KEGG; nta:107812972; -.
DR   OMA; HYERDKT; -.
DR   OrthoDB; 1566561at2759; -.
DR   PhylomeDB; P49099; -.
DR   Proteomes; UP000084051; Unplaced.
DR   GO; GO:0005789; C:endoplasmic reticulum membrane; IEA:UniProtKB-SubCell.
DR   GO; GO:0016021; C:integral component of membrane; IEA:UniProtKB-KW.
DR   GO; GO:0043231; C:intracellular membrane-bounded organelle; IBA:GO_Central.
DR   GO; GO:0016020; C:membrane; IBA:GO_Central.
DR   GO; GO:0020037; F:heme binding; IBA:GO_Central.
DR   GO; GO:0046872; F:metal ion binding; IEA:UniProtKB-KW.
DR   Gene3D; 3.10.120.10; -; 1.
DR   InterPro; IPR001199; Cyt_B5-like_heme/steroid-bd.
DR   InterPro; IPR036400; Cyt_B5-like_heme/steroid_sf.
DR   InterPro; IPR018506; Cyt_B5_heme-BS.
DR   Pfam; PF00173; Cyt-b5; 1.
DR   PRINTS; PR00363; CYTOCHROMEB5.
DR   SMART; SM01117; Cyt-b5; 1.
DR   SUPFAM; SSF55856; SSF55856; 1.
DR   PROSITE; PS00191; CYTOCHROME_B5_1; 1.
DR   PROSITE; PS50255; CYTOCHROME_B5_2; 1.
PE   2: Evidence at transcript level;
KW   Electron transport; Endoplasmic reticulum; Heme; Iron; Membrane;
KW   Metal-binding; Microsome; Reference proteome; Transmembrane;
KW   Transmembrane helix; Transport.
FT   CHAIN           1..135
FT                   /note="Cytochrome b5, seed isoform"
FT                   /id="PRO_0000166026"
FT   TRANSMEM        107..127
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   DOMAIN          5..81
FT                   /note="Cytochrome b5 heme-binding"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00279"
FT   BINDING         40
FT                   /ligand="heme"
FT                   /ligand_id="ChEBI:CHEBI:30413"
FT                   /ligand_part="Fe"
FT                   /ligand_part_id="ChEBI:CHEBI:18248"
FT                   /note="axial binding residue"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00279"
FT   BINDING         64
FT                   /ligand="heme"
FT                   /ligand_id="ChEBI:CHEBI:30413"
FT                   /ligand_part="Fe"
FT                   /ligand_part_id="ChEBI:CHEBI:18248"
FT                   /note="axial binding residue"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00279"
SQ   SEQUENCE   135 AA;  14869 MW;  A36CCA081A72ECBC CRC64;
     MGGQSKVFTL AEVSNHNNAK DCWLIISGKV YNVTKFLEDH PGGGEVLLSA TGKDATDDFE
     DIGHSSSARA MLDEYYVGDI DSSTIPTKVK YTPPKQPHYN QDKTTEFIVK LLQFLVPLII
     LGVAFGVHFY TKQSA