ID   HMT3_MAIZE              Reviewed;         338 AA.
AC   Q9FUM8;
DT   19-JUL-2004, integrated into UniProtKB/Swiss-Prot.
DT   01-MAR-2001, sequence version 1.
DT   03-AUG-2022, entry version 96.
DE   RecName: Full=Homocysteine S-methyltransferase 3;
DE            EC=2.1.1.10;
DE   AltName: Full=S-methylmethionine:homocysteine methyltransferase 3;
DE            Short=SMM:Hcy S-methyltransferase 3;
DE   AltName: Full=ZmHMT-3;
GN   Name=HMT-3;
OS   Zea mays (Maize).
OC   Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta;
OC   Spermatophyta; Magnoliopsida; Liliopsida; Poales; Poaceae; PACMAD clade;
OC   Panicoideae; Andropogonodae; Andropogoneae; Tripsacinae; Zea.
OX   NCBI_TaxID=4577;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA].
RX   PubMed=11309147; DOI=10.1046/j.1365-313x.2001.00988.x;
RA   Ranocha P., McNeil S.D., Ziemak M.J., Li C., Tarczynski M.C., Hanson A.D.;
RT   "The S-methylmethionine cycle in angiosperms: ubiquity, antiquity and
RT   activity.";
RL   Plant J. 25:575-584(2001).
CC   -!- FUNCTION: Catalyzes methyl transfer from S-methylmethionine (SMM) to
CC       adenosyl-L-homocysteine (AdoMet). SMM degradation (by HMT-1, HMT-2,
CC       HMT-3 and HMT-4) and biosynthesis (by MMT1) constitute the SMM cycle in
CC       plants, which is probably required to achieve short term control of
CC       AdoMet level (By similarity). {ECO:0000250}.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=L-homocysteine + S-methyl-L-methionine = H(+) + 2 L-
CC         methionine; Xref=Rhea:RHEA:26337, ChEBI:CHEBI:15378,
CC         ChEBI:CHEBI:57844, ChEBI:CHEBI:58199, ChEBI:CHEBI:58252; EC=2.1.1.10;
CC   -!- COFACTOR:
CC       Name=Zn(2+); Xref=ChEBI:CHEBI:29105;
CC         Evidence={ECO:0000255|PROSITE-ProRule:PRU00333};
CC   -!- SUBUNIT: Monomer. {ECO:0000250}.
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DR   EMBL; AF297046; AAG22539.1; -; mRNA.
DR   RefSeq; NP_001105013.1; NM_001111543.2.
DR   AlphaFoldDB; Q9FUM8; -.
DR   SMR; Q9FUM8; -.
DR   STRING; 4577.GRMZM2G152470_P01; -.
DR   PaxDb; Q9FUM8; -.
DR   EnsemblPlants; Zm00001eb135800_T002; Zm00001eb135800_P002; Zm00001eb135800.
DR   GeneID; 541875; -.
DR   Gramene; Zm00001eb135800_T002; Zm00001eb135800_P002; Zm00001eb135800.
DR   KEGG; zma:541875; -.
DR   eggNOG; KOG1579; Eukaryota.
DR   HOGENOM; CLU_004914_3_2_1; -.
DR   OMA; TAVINTH; -.
DR   OrthoDB; 731388at2759; -.
DR   Proteomes; UP000007305; Chromosome 3.
DR   ExpressionAtlas; Q9FUM8; baseline and differential.
DR   Genevisible; Q9FUM8; ZM.
DR   GO; GO:0047150; F:betaine-homocysteine S-methyltransferase activity; IEA:InterPro.
DR   GO; GO:0061627; F:S-methylmethionine-homocysteine S-methyltransferase activity; IEA:RHEA.
DR   GO; GO:0008270; F:zinc ion binding; IEA:InterPro.
DR   GO; GO:0009086; P:methionine biosynthetic process; IEA:UniProtKB-KW.
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   2: Evidence at transcript level;
KW   Amino-acid biosynthesis; Metal-binding; Methionine biosynthesis;
KW   Methyltransferase; Reference proteome; S-adenosyl-L-methionine;
KW   Transferase; Zinc.
FT   CHAIN           1..338
FT                   /note="Homocysteine S-methyltransferase 3"
FT                   /id="PRO_0000114616"
FT   DOMAIN          12..326
FT                   /note="Hcy-binding"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00333"
FT   BINDING         244
FT                   /ligand="Zn(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29105"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00333"
FT   BINDING         311
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"
SQ   SEQUENCE   338 AA;  36757 MW;  9C787F9F10D794E2 CRC64;
     MVGTAEGGAE RAVRRWVDAA GGRLVLDGGL ATELEANGAD LNDPLWSAKC LLSSPHLIRK
     VHMDYLEAGA NIIITASYQA TIQGFESKGF SKEQSENLLT KSVQIALEAR EMFLKEHLEK
     STPIQHPILV AAALGSYGAY LADGSEYSGD YGEAGTKEFL KDFHRRRLQV LAEAGPDLIA
     FETIPNKLEA QAYVELLEEC NINIPSWLSF NSKDGVHVVS GDSLIECATI ADKCAKVGAV
     GINCTPPRFI HGLILSIRKV TDKPILIYPN SGERYDGEKK EWVESTGVSD GDFVSYVNEW
     CKDGAALIGG CCRTTPNTIR AIHRTLNQGC HKHQLPVA