ID   TRXR1_EMIHU             Reviewed;         495 AA.
AC   B9A1H3;
DT   20-APR-2010, integrated into UniProtKB/Swiss-Prot.
DT   24-MAR-2009, sequence version 1.
DT   03-AUG-2022, entry version 51.
DE   RecName: Full=Thioredoxin reductase SEP1;
DE            Short=EhSEP1 {ECO:0000303|PubMed:18945673};
DE            EC=1.8.1.9;
GN   Name=SEP1;
OS   Emiliania huxleyi (Coccolithophore) (Pontosphaera huxleyi).
OC   Eukaryota; Haptista; Haptophyta; Prymnesiophyceae; Isochrysidales;
OC   Noelaerhabdaceae; Emiliania.
OX   NCBI_TaxID=2903;
RN   [1] {ECO:0000305, ECO:0000312|EMBL:BAH20464.1}
RP   NUCLEOTIDE SEQUENCE [MRNA], PROTEIN SEQUENCE OF 25-35 AND 169-180, ACTIVITY
RP   REGULATION, BLOCKAGE OF N-TERMINUS, AND PRESENCE OF SELENOCYSTEINE.
RC   STRAIN=NIES-837 / EH-2 {ECO:0000269|PubMed:18945673};
RX   PubMed=18945673; DOI=10.1074/jbc.m805472200;
RA   Araie H., Suzuki I., Shiraiwa Y.;
RT   "Identification and characterization of a selenoprotein, thioredoxin
RT   reductase, in a unicellular marine haptophyte alga, Emiliania huxleyi.";
RL   J. Biol. Chem. 283:35329-35336(2008).
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=[thioredoxin]-dithiol + NADP(+) = [thioredoxin]-disulfide +
CC         H(+) + NADPH; Xref=Rhea:RHEA:20345, Rhea:RHEA-COMP:10698, Rhea:RHEA-
CC         COMP:10700, ChEBI:CHEBI:15378, ChEBI:CHEBI:29950, ChEBI:CHEBI:50058,
CC         ChEBI:CHEBI:57783, ChEBI:CHEBI:58349; EC=1.8.1.9;
CC         Evidence={ECO:0000305};
CC   -!- COFACTOR:
CC       Name=FAD; Xref=ChEBI:CHEBI:57692;
CC         Evidence={ECO:0000250|UniProtKB:Q16881};
CC       Note=Binds 1 FAD per subunit. {ECO:0000250|UniProtKB:Q16881};
CC   -!- ACTIVITY REGULATION: Activity was very low in selenium-depleted cells,
CC       but increased 4-fold to the same level as in selenium-sufficient cells
CC       for 70 hours after the addition of 10 nm selenite.
CC       {ECO:0000269|PubMed:18945673}.
CC   -!- SUBUNIT: Homodimer. {ECO:0000250|UniProtKB:Q16881}.
CC   -!- PTM: The N-terminus is blocked. {ECO:0000269|PubMed:18945673}.
CC   -!- MISCELLANEOUS: The thioredoxin reductase active site is a redox-active
CC       disulfide bond. The selenocysteine residue is also essential for
CC       catalytic activity. {ECO:0000269|PubMed:18945673}.
CC   -!- SIMILARITY: Belongs to the class-I pyridine nucleotide-disulfide
CC       oxidoreductase family. {ECO:0000305}.
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DR   EMBL; AB379907; BAH20464.1; -; mRNA.
DR   STRING; 2903.EOD04034; -.
DR   eggNOG; KOG4716; Eukaryota.
DR   BRENDA; 1.8.1.9; 2068.
DR   Proteomes; UP000013827; Unassembled WGS sequence.
DR   GO; GO:0050660; F:flavin adenine dinucleotide binding; IEA:InterPro.
DR   GO; GO:0004791; F:thioredoxin-disulfide reductase activity; IEA:UniProtKB-EC.
DR   GO; GO:0045454; P:cell redox homeostasis; IEA:InterPro.
DR   Gene3D; 3.30.390.30; -; 1.
DR   Gene3D; 3.50.50.60; -; 2.
DR   InterPro; IPR036188; FAD/NAD-bd_sf.
DR   InterPro; IPR023753; FAD/NAD-binding_dom.
DR   InterPro; IPR016156; FAD/NAD-linked_Rdtase_dimer_sf.
DR   InterPro; IPR001100; Pyr_nuc-diS_OxRdtase.
DR   InterPro; IPR004099; Pyr_nucl-diS_OxRdtase_dimer.
DR   InterPro; IPR012999; Pyr_OxRdtase_I_AS.
DR   InterPro; IPR006338; Thioredoxin/glutathione_Rdtase.
DR   Pfam; PF07992; Pyr_redox_2; 1.
DR   Pfam; PF02852; Pyr_redox_dim; 1.
DR   PIRSF; PIRSF000350; Mercury_reductase_MerA; 1.
DR   SUPFAM; SSF51905; SSF51905; 1.
DR   SUPFAM; SSF55424; SSF55424; 1.
DR   TIGRFAMs; TIGR01438; TGR; 1.
DR   PROSITE; PS00076; PYRIDINE_REDOX_1; 1.
PE   1: Evidence at protein level;
KW   Direct protein sequencing; Disulfide bond; FAD; Flavoprotein; NADP;
KW   Oxidoreductase; Redox-active center; Reference proteome; Selenium;
KW   Selenocysteine.
FT   CHAIN           1..495
FT                   /note="Thioredoxin reductase SEP1"
FT                   /id="PRO_0000393868"
FT   ACT_SITE        468
FT                   /note="Proton acceptor"
FT                   /evidence="ECO:0000250|UniProtKB:Q16881"
FT   BINDING         37..54
FT                   /ligand="FAD"
FT                   /ligand_id="ChEBI:CHEBI:57692"
FT                   /evidence="ECO:0000250|UniProtKB:Q16881"
FT   NON_STD         494
FT                   /note="Selenocysteine"
FT                   /evidence="ECO:0000269|PubMed:18945673"
FT   DISULFID        54..59
FT                   /note="Redox-active"
FT                   /evidence="ECO:0000250|UniProtKB:Q16881"
FT   CROSSLNK        493..494
FT                   /note="Cysteinyl-selenocysteine (Cys-Sec)"
FT                   /evidence="ECO:0000250|UniProtKB:Q16881"
SQ   SEQUENCE   495 AA;  52206 MW;  D69A816303A54278 CRC64;
     MAAAEAQYDL LVIGGGSGGL ACSKRAASHG KKVAVCDFVK PSPPGTTWGL GGTCVNVGCI
     PKKLMHQAAL LGEGMTDAES FGWEVAAPKH NWETMVGNVQ GHIKSLNFGY RSDLMSNGVK
     YYNAYATFLD PHTVEAVDKK GKVTKITASE IVICTGGRPR YPDIPGAKEL GITSDDVFAL
     KSPPGRTLVV GASYVALECA GFIKGVGYDT TVMMRSIPLR GFDQQMAGLC KTYMQEHGVA
     FIEGAVPTAV EATPSGAKKV SWKLADGSVG SGEYDTVLFA IGRDVCTSAI GIDKAGVKLS
     SNGKVPTVNE QTNVPHIYAI GDIIDGEALN PPSATTELTP VAIQAGKLLA DRLYAGKSAL
     MDYSMVATTV YTPLEYGAVG LPEEEAIKLH GEDNIEVYHS YFKPLEWTLP HRGDNVCYAK
     LICLKPEGER VIGLHVCGPN AGEMTQGFAV AIKAGATKAH FDDTVGIHPT VAEEFTLLAA
     TKRSGDSAEK SGCUG