ID   CYB5_TOBAC              Reviewed;         136 AA.
AC   P49098;
DT   01-FEB-1996, integrated into UniProtKB/Swiss-Prot.
DT   01-FEB-1996, sequence version 1.
DT   03-AUG-2022, entry version 102.
DE   RecName: Full=Cytochrome b5;
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   TISSUE=Leaf;
RX   PubMed=8049375; DOI=10.1007/bf00043880;
RA   Smith M.A., Stobart A.K., Shewry P.R., Napier J.A.;
RT   "Tobacco cytochrome b5: cDNA isolation, expression analysis and in vitro
RT   protein targeting.";
RL   Plant Mol. Biol. 25:527-537(1994).
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. Is involved in the reduction of
CC       cytochrome P-450 and may therefore be involved in flavonoid
CC       biosynthesis in the petals.
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: Is highly expressed in developing seeds, moderately
CC       expressed in flowers, and is expressed at low levels in the leaf.
CC   -!- SIMILARITY: Belongs to the cytochrome b5 family. {ECO:0000305}.
CC   -!- SEQUENCE CAUTION:
CC       Sequence=CAA50575.1; Type=Erroneous initiation; Evidence={ECO:0000305};
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DR   EMBL; X71441; CAA50575.1; ALT_INIT; mRNA.
DR   EMBL; X68140; CAA48240.1; -; mRNA.
DR   PIR; S46306; S46306.
DR   RefSeq; XP_016457294.1; XM_016601808.1.
DR   RefSeq; XP_016498088.1; XM_016642602.1.
DR   AlphaFoldDB; P49098; -.
DR   SMR; P49098; -.
DR   STRING; 4097.P49098; -.
DR   GeneID; 107781159; -.
DR   GeneID; 107816859; -.
DR   KEGG; nta:107781159; -.
DR   KEGG; nta:107816859; -.
DR   OMA; SKDCWIV; -.
DR   OrthoDB; 1566561at2759; -.
DR   PhylomeDB; P49098; -.
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..136
FT                   /note="Cytochrome b5"
FT                   /id="PRO_0000166025"
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"
FT   CONFLICT        10..11
FT                   /note="LA -> EF (in Ref. 1; CAA48240)"
FT                   /evidence="ECO:0000305"
FT   CONFLICT        105
FT                   /note="Missing (in Ref. 1; CAA48240)"
FT                   /evidence="ECO:0000305"
SQ   SEQUENCE   136 AA;  14979 MW;  DACE9EA695B2835F CRC64;
     MGGETKVFTL AEVSQHNNAK DCWLVISGKV YDVTKFLDDH PGGDEVLLSA TGKDATDDFE
     DVGHSSSARA MLDEYYVGDI DSATIPTKTK YTPPNQPHYN QDKTSEFVVK LLQFLVPLII
     LGVAFGIRFY TKQSSA