ID   SMTA_ASTBI              Reviewed;         338 AA.
AC   P56707; Q9ZRT7;
DT   15-JUL-1999, integrated into UniProtKB/Swiss-Prot.
DT   15-JUL-1999, sequence version 1.
DT   03-AUG-2022, entry version 70.
DE   RecName: Full=Selenocysteine methyltransferase;
DE            Short=SECYS-MT;
DE            Short=SECYS-methyltransferase;
DE            EC=2.1.1.280;
GN   Name=SMTA;
OS   Astragalus bisulcatus (Two-grooved milkvetch) (Phaca bisulcata).
OC   Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta;
OC   Spermatophyta; Magnoliopsida; eudicotyledons; Gunneridae; Pentapetalae;
OC   rosids; fabids; Fabales; Fabaceae; Papilionoideae; 50 kb inversion clade;
OC   NPAAA clade; Hologalegina; IRL clade; Galegeae; Astragalus.
OX   NCBI_TaxID=20406;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA], PROTEIN SEQUENCE OF 80-100; 126-135; 170-184;
RP   189-202; 214-232; 264-179 AND 282-300, IDENTIFICATION OF METHYL DONOR, AND
RP   TISSUE SPECIFICITY.
RX   PubMed=10026151; DOI=10.1074/jbc.274.9.5407;
RA   Neuhierl B., Thanbichler M., Lottspeich F., Boeck A.;
RT   "A family of S-methylmethionine-dependent thiol/selenol methyltransferases.
RT   Role in selenium tolerance and evolutionary relation.";
RL   J. Biol. Chem. 274:5407-5414(1999).
RN   [2]
RP   CATALYTIC ACTIVITY, SUBUNIT, AND BIOPHYSICOCHEMICAL PROPERTIES.
RX   PubMed=8706715; DOI=10.1111/j.1432-1033.1996.0235u.x;
RA   Neuhierl B., Boeck A.;
RT   "On the mechanism of selenium tolerance in selenium-accumulating plants.
RT   Purification and characterization of a specific selenocysteine
RT   methyltransferase from cultured cells of Astragalus bisculatus.";
RL   Eur. J. Biochem. 239:235-238(1996).
CC   -!- FUNCTION: Catalyzes the methylation of selenocysteine with S-
CC       methylmethionine as donor. Does not methylate cysteine.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=L-selenocysteine + S-methyl-L-methionine = H(+) + L-methionine
CC         + Se-methyl-L-selenocysteine; Xref=Rhea:RHEA:26341,
CC         ChEBI:CHEBI:15378, ChEBI:CHEBI:57843, ChEBI:CHEBI:57844,
CC         ChEBI:CHEBI:58252, ChEBI:CHEBI:58531; EC=2.1.1.280;
CC         Evidence={ECO:0000269|PubMed:8706715};
CC   -!- COFACTOR:
CC       Name=Zn(2+); Xref=ChEBI:CHEBI:29105;
CC         Evidence={ECO:0000255|PROSITE-ProRule:PRU00333};
CC   -!- BIOPHYSICOCHEMICAL PROPERTIES:
CC       Kinetic parameters:
CC         KM=0.015 mM for S-adenosyl-L-methionine {ECO:0000269|PubMed:8706715};
CC         KM=0.7 mM for L-selenocysteine {ECO:0000269|PubMed:8706715};
CC         KM=0.35 mM for DL-selenohomocysteine {ECO:0000269|PubMed:8706715};
CC       pH dependence:
CC         Optimum pH is 6.0. {ECO:0000269|PubMed:8706715};
CC   -!- SUBUNIT: Monomer. {ECO:0000269|PubMed:8706715}.
CC   -!- TISSUE SPECIFICITY: Present in all tissues tested.
CC       {ECO:0000269|PubMed:10026151}.
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DR   EMBL; AJ131433; CAA10368.1; -; mRNA.
DR   PIR; T51940; T51940.
DR   AlphaFoldDB; P56707; -.
DR   SMR; P56707; -.
DR   KEGG; ag:CAA10368; -.
DR   BioCyc; MetaCyc:MON-15257; -.
DR   BRENDA; 2.1.1.280; 557.
DR   SABIO-RK; P56707; -.
DR   GO; GO:0047150; F:betaine-homocysteine S-methyltransferase activity; IEA:InterPro.
DR   GO; GO:0016205; F:selenocysteine methyltransferase activity; IEA:UniProtKB-EC.
DR   GO; GO:0008270; F:zinc ion binding; IEA:InterPro.
DR   GO; GO:0009086; P:methionine biosynthetic process; IEA:InterPro.
DR   GO; GO:0032259; P:methylation; IEA:UniProtKB-KW.
DR   Gene3D; 3.20.20.330; -; 1.
DR   InterPro; IPR017226; Betaine-hCys_S-MeTrfase_BHMT.
DR   InterPro; IPR003726; HCY_dom.
DR   InterPro; IPR036589; HCY_dom_sf.
DR   Pfam; PF02574; S-methyl_trans; 1.
DR   PIRSF; PIRSF037505; Betaine_HMT; 1.
DR   SUPFAM; SSF82282; SSF82282; 1.
DR   PROSITE; PS50970; HCY; 1.
PE   1: Evidence at protein level;
KW   Direct protein sequencing; Metal-binding; Methyltransferase; Transferase;
KW   Zinc.
FT   CHAIN           1..338
FT                   /note="Selenocysteine methyltransferase"
FT                   /id="PRO_0000114620"
FT   DOMAIN          1..327
FT                   /note="Hcy-binding"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00333"
FT   BINDING         245
FT                   /ligand="Zn(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29105"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00333"
FT   BINDING         312
FT                   /ligand="Zn(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29105"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00333"
FT   BINDING         313
FT                   /ligand="Zn(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29105"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00333"
SQ   SEQUENCE   338 AA;  36714 MW;  BDE604F49AFAF8A5 CRC64;
     MSSPLITDFL HQAGRAAVIA GGLGTELQRH GADLNDPLWS AKCLLSCPHL IRQVHLDYLE
     NGADIIITAS YQATIQGFKA KGFSDEEGEA LLRRSVEIAR EARDLYYQRC AESSSDNGDD
     SRILKQRPIL IAGSVGSYGA YLADGSEFSG NYGDAIKSET LKDFHRRKVQ ILADSGVDLL
     AFEAVPNKLE AQAYADLLEE ENIITPAWFA FTSKDGNNVV SGDSIEECGS IAESCDKVVA
     VGINCTPPRF IHDLILLLKK VTAKPIVIYP NSGETYDAIR KEWGQNSGVT DEDFVSYVDK
     WCESGASLVG GCCRTTPDTI RGIYKILSSG QSPTFSAK