AC   MF_01283;
DC   Protein; auto
TR   HAMAP; MF_01283; -; 1; level=0
XX
Names: RibBA
XX
ID   RIBBA
DE   RecName: Full=Riboflavin biosynthesis protein RibBA;
DE   Includes:
DE     RecName: Full=3,4-dihydroxy-2-butanone 4-phosphate synthase;
DE              Short=DHBP synthase;
DE              EC=4.1.99.12;
DE   Includes:
DE     RecName: Full=GTP cyclohydrolase-2;
DE              EC=3.5.4.25;
DE     AltName: Full=GTP cyclohydrolase II;
GN   Name=ribBA;
XX
CC   -!- FUNCTION: Catalyzes the conversion of D-ribulose 5-phosphate to formate
CC       and 3,4-dihydroxy-2-butanone 4-phosphate.
CC   -!- FUNCTION: Catalyzes the conversion of GTP to 2,5-diamino-6-
CC       ribosylamino-4(3H)-pyrimidinone 5'-phosphate (DARP), formate and
CC       pyrophosphate.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=D-ribulose 5-phosphate = (2S)-2-hydroxy-3-oxobutyl phosphate +
CC         formate + H(+); Xref=Rhea:RHEA:18457, ChEBI:CHEBI:15378,
CC         ChEBI:CHEBI:15740, ChEBI:CHEBI:58121, ChEBI:CHEBI:58830;
CC         EC=4.1.99.12;
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=GTP + 4 H2O = 2,5-diamino-6-hydroxy-4-(5-phosphoribosylamino)-
CC         pyrimidine + formate + 3 H(+) + 2 phosphate; Xref=Rhea:RHEA:23704,
CC         ChEBI:CHEBI:15377, ChEBI:CHEBI:15378, ChEBI:CHEBI:15740,
CC         ChEBI:CHEBI:37565, ChEBI:CHEBI:43474, ChEBI:CHEBI:58614; EC=3.5.4.25;
CC   -!- COFACTOR:
CC       Name=Mg(2+); Xref=ChEBI:CHEBI:18420;
CC       Name=Mn(2+); Xref=ChEBI:CHEBI:29035;
CC       Note=Binds 2 divalent metal cations per subunit. Magnesium or
CC       manganese.;
CC   -!- COFACTOR:
CC       Name=Zn(2+); Xref=ChEBI:CHEBI:29105;
CC       Note=Binds 1 zinc ion per subunit.;
CC   -!- PATHWAY: Cofactor biosynthesis; riboflavin biosynthesis; 2-hydroxy-3-
CC       oxobutyl phosphate from D-ribulose 5-phosphate: step 1/1.
CC   -!- PATHWAY: Cofactor biosynthesis; riboflavin biosynthesis; 5-amino-6-(D-
CC       ribitylamino)uracil from GTP: step 1/4.
CC   -!- SIMILARITY: In the N-terminal section; belongs to the DHBP synthase
CC       family.
CC   -!- SIMILARITY: In the C-terminal section; belongs to the GTP
CC       cyclohydrolase II family.
XX
DR   Pfam; PF00926; DHBP_synthase; 1; trigger=no
DR   Pfam; PF00925; GTP_cyclohydro2; 1; trigger=no
DR   NCBIfam; TIGR00505; RibA; 1; trigger=no
DR   NCBIfam; TIGR00506; RibB; 1; trigger=no
XX
KW   GTP-binding
KW   Hydrolase
KW   Lyase
KW   Magnesium
KW   Manganese
KW   Metal-binding
KW   Multifunctional enzyme
KW   Nucleotide-binding
KW   Riboflavin biosynthesis
KW   Zinc
XX
GO   GO:0000287; F:magnesium ion binding
GO   GO:0003935; F:GTP cyclohydrolase II activity
GO   GO:0008270; F:zinc ion binding
GO   GO:0008686; F:3,4-dihydroxy-2-butanone-4-phosphate synthase activity
GO   GO:0030145; F:manganese ion binding
GO   GO:0009231; P:riboflavin biosynthetic process
XX
FT   From: RIBBA_BACSU (P17620)
FT   BINDING         251..255
FT                   /ligand="GTP"
FT                   /ligand_id="ChEBI:CHEBI:37565"
FT   BINDING         294..296
FT                   /ligand="GTP"
FT                   /ligand_id="ChEBI:CHEBI:37565"
FT   Condition: E-G-R
FT   REGION          Nter..199
FT                   /note="DHBP synthase"
FT   BINDING         26..27
FT                   /ligand="D-ribulose 5-phosphate"
FT                   /ligand_id="ChEBI:CHEBI:58121"
FT   Condition: R-E
FT   BINDING         138..142
FT                   /ligand="D-ribulose 5-phosphate"
FT                   /ligand_id="ChEBI:CHEBI:58121"
FT   Condition: R-x-x-H-T
FT   REGION          200..Cter
FT                   /note="GTP cyclohydrolase II"
FT   ACT_SITE        328
FT                   /note="Proton acceptor; for GTP cyclohydrolase activity"
FT   Condition: D
FT   ACT_SITE        330
FT                   /note="Nucleophile; for GTP cyclohydrolase activity"
FT   Condition: R
FT   BINDING         27
FT                   /ligand="Mg(2+)"
FT                   /ligand_id="ChEBI:CHEBI:18420"
FT                   /ligand_label="1"
FT   Condition: E
FT   BINDING         27
FT                   /ligand="Mg(2+)"
FT                   /ligand_id="ChEBI:CHEBI:18420"
FT                   /ligand_label="2"
FT   Condition: E
FT   BINDING         141
FT                   /ligand="Mg(2+)"
FT                   /ligand_id="ChEBI:CHEBI:18420"
FT                   /ligand_label="2"
FT   Condition: H
FT   BINDING         256
FT                   /ligand="Zn(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29105"
FT                   /ligand_note="catalytic"
FT   Condition: C
FT   BINDING         267
FT                   /ligand="Zn(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29105"
FT                   /ligand_note="catalytic"
FT   Condition: C
FT   BINDING         269
FT                   /ligand="Zn(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29105"
FT                   /ligand_note="catalytic"
FT   Condition: C
FT   BINDING         31
FT                   /ligand="D-ribulose 5-phosphate"
FT                   /ligand_id="ChEBI:CHEBI:58121"
FT   Condition: D
FT   BINDING         162
FT                   /ligand="D-ribulose 5-phosphate"
FT                   /ligand_id="ChEBI:CHEBI:58121"
FT   Condition: E
FT   BINDING         272
FT                   /ligand="GTP"
FT                   /ligand_id="ChEBI:CHEBI:37565"
FT   Condition: Q
FT   BINDING         316
FT                   /ligand="GTP"
FT                   /ligand_id="ChEBI:CHEBI:37565"
FT   Condition: T
FT   BINDING         351
FT                   /ligand="GTP"
FT                   /ligand_id="ChEBI:CHEBI:37565"
FT   Condition: [TS]
FT   BINDING         356
FT                   /ligand="GTP"
FT                   /ligand_id="ChEBI:CHEBI:37565"
FT   Condition: K
FT   SITE            124
FT                   /note="Essential for DHBP synthase activity"
FT   Condition: H
FT   SITE            162
FT                   /note="Essential for DHBP synthase activity"
FT   Condition: E
XX
Size: 388-425;
Related: MF_00178; MF_00179;
Template: P50855;
Scope:
 Bacteria
Fusion:
 Nter: None
 Cter: <Unknown>
Duplicate: None
Plasmid: None
Comments: RibA and RibB are not fused in some organisms (see MF_00179 for RibA and MF_00180 for RibB).
 Fused with an unknown C-terminal domain in SYNY3.
XX
# Revision 1.20 2023/06/01
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