ID   RISB_SACI1              Reviewed;         154 AA.
AC   C3NGF3;
DT   22-SEP-2009, integrated into UniProtKB/Swiss-Prot.
DT   16-JUN-2009, sequence version 1.
DT   04-NOV-2026, entry version 75.
DE   RecName: Full=6,7-dimethyl-8-ribityllumazine synthase {ECO:0000255|HAMAP-Rule:MF_00178};
DE            Short=DMRL synthase {ECO:0000255|HAMAP-Rule:MF_00178};
DE            Short=LS {ECO:0000255|HAMAP-Rule:MF_00178};
DE            Short=Lumazine synthase {ECO:0000255|HAMAP-Rule:MF_00178};
DE            EC=2.5.1.78 {ECO:0000255|HAMAP-Rule:MF_00178};
GN   Name=ribH {ECO:0000255|HAMAP-Rule:MF_00178};
GN   OrderedLocusNames=YN1551_1107;
OS   Saccharolobus islandicus (strain Y.N.15.51 / Yellowstone #2) (Sulfolobus
OS   islandicus).
OC   Archaea; Thermoproteota; Thermoprotei; Sulfolobales; Sulfolobaceae;
OC   Saccharolobus.
OX   NCBI_TaxID=419942;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
RC   STRAIN=Y.N.15.51 / Yellowstone #2;
RX   PubMed=19435847; DOI=10.1073/pnas.0808945106;
RA   Reno M.L., Held N.L., Fields C.J., Burke P.V., Whitaker R.J.;
RT   "Biogeography of the Sulfolobus islandicus pan-genome.";
RL   Proc. Natl. Acad. Sci. U.S.A. 106:8605-8610(2009).
CC   -!- FUNCTION: Catalyzes the formation of 6,7-dimethyl-8-ribityllumazine by
CC       condensation of 5-amino-6-(D-ribitylamino)uracil with 3,4-dihydroxy-2-
CC       butanone 4-phosphate. This is the penultimate step in the biosynthesis
CC       of riboflavin. {ECO:0000255|HAMAP-Rule:MF_00178}.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=(2S)-2-hydroxy-3-oxobutyl phosphate + 5-amino-6-(D-
CC         ribitylamino)uracil = 6,7-dimethyl-8-(1-D-ribityl)lumazine +
CC         phosphate + 2 H2O + H(+); Xref=Rhea:RHEA:26152, ChEBI:CHEBI:15377,
CC         ChEBI:CHEBI:15378, ChEBI:CHEBI:15934, ChEBI:CHEBI:43474,
CC         ChEBI:CHEBI:58201, ChEBI:CHEBI:58830; EC=2.5.1.78;
CC         Evidence={ECO:0000255|HAMAP-Rule:MF_00178};
CC   -!- PATHWAY: Cofactor biosynthesis; riboflavin biosynthesis; riboflavin
CC       from 2-hydroxy-3-oxobutyl phosphate and 5-amino-6-(D-
CC       ribitylamino)uracil: step 1/2. {ECO:0000255|HAMAP-Rule:MF_00178}.
CC   -!- SIMILARITY: Belongs to the DMRL synthase family. {ECO:0000255|HAMAP-
CC       Rule:MF_00178}.
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DR   EMBL; CP001404; ACP48213.1; -; Genomic_DNA.
DR   RefSeq; WP_012713917.1; NC_012623.1.
DR   AlphaFoldDB; C3NGF3; -.
DR   SMR; C3NGF3; -.
DR   GeneID; 65564508; -.
DR   GeneID; 7810838; -.
DR   KEGG; sin:YN1551_1107; -.
DR   HOGENOM; CLU_089358_3_1_2; -.
DR   OMA; AAIKMCD; -.
DR   UniPathway; UPA00275; UER00404.
DR   GO; GO:0009349; C:riboflavin synthase complex; IEA:InterPro.
DR   GO; GO:0000906; F:6,7-dimethyl-8-ribityllumazine synthase activity; IEA:UniProtKB-UniRule.
DR   GO; GO:0009231; P:riboflavin biosynthetic process; IEA:UniProtKB-UniRule.
DR   CDD; cd09211; Lumazine_synthase_archaeal; 1.
DR   FunFam; 3.40.50.960:FF:000003; 6,7-dimethyl-8-ribityllumazine synthase; 1.
DR   Gene3D; 3.40.50.960; Lumazine/riboflavin synthase; 1.
DR   HAMAP; MF_00178; Lumazine_synth; 1.
DR   InterPro; IPR034964; LS.
DR   InterPro; IPR002180; LS/RS.
DR   InterPro; IPR036467; LS/RS_sf.
DR   NCBIfam; TIGR00114; lumazine-synth; 1.
DR   PANTHER; PTHR21058:SF0; 6,7-DIMETHYL-8-RIBITYLLUMAZINE SYNTHASE; 1.
DR   PANTHER; PTHR21058; 6,7-DIMETHYL-8-RIBITYLLUMAZINE SYNTHASE DMRL SYNTHASE LUMAZINE SYNTHASE; 1.
DR   Pfam; PF00885; DMRL_synthase; 1.
DR   SUPFAM; SSF52121; Lumazine synthase; 1.
PE   3: Inferred from homology;
KW   Riboflavin biosynthesis; Transferase.
FT   CHAIN           1..154
FT                   /note="6,7-dimethyl-8-ribityllumazine synthase"
FT                   /id="PRO_1000203804"
FT   ACT_SITE        79
FT                   /note="Proton donor"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00178"
FT   BINDING         15
FT                   /ligand="5-amino-6-(D-ribitylamino)uracil"
FT                   /ligand_id="ChEBI:CHEBI:15934"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00178"
FT   BINDING         47..49
FT                   /ligand="5-amino-6-(D-ribitylamino)uracil"
FT                   /ligand_id="ChEBI:CHEBI:15934"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00178"
FT   BINDING         71..73
FT                   /ligand="5-amino-6-(D-ribitylamino)uracil"
FT                   /ligand_id="ChEBI:CHEBI:15934"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00178"
FT   BINDING         76..77
FT                   /ligand="(2S)-2-hydroxy-3-oxobutyl phosphate"
FT                   /ligand_id="ChEBI:CHEBI:58830"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00178"
FT   BINDING         104
FT                   /ligand="5-amino-6-(D-ribitylamino)uracil"
FT                   /ligand_id="ChEBI:CHEBI:15934"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00178"
FT   BINDING         119
FT                   /ligand="(2S)-2-hydroxy-3-oxobutyl phosphate"
FT                   /ligand_id="ChEBI:CHEBI:58830"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00178"
SQ   SEQUENCE   154 AA;  17163 MW;  AB2FC15E77276D26 CRC64;
     MQEKSIRLGI VVAEFNYDIT QLMLQKALSH AKFLNAEVKV VIKVPGTFDM PLAIKKLLEK
     DFIDAVVTLG AVIKGETKHD EIVASQTARK IVDLSTEFNK PVTLGIIGHG ATHEQAVERI
     EEYATRAVEA AIKLVQRTRK IDELKEVKET VIID
//