HAMAP

Accession	MF_01283
Dates	16-NOV-2007 (Created) 27-SEP-2010 (Last updated, Version 7)

Data class

Protein

Predictors

HAMAP; MF_01283; [distribution of match scores in UniProtKB];[seed alignment for MF_01283]

Names

RibBA

Identifier

RIBBA

Protein name

RecName: Full=Riboflavin biosynthesis protein ribBA; RecName: Full=3,4-dihydroxy-2-butanone 4-phosphate synthase; Short=DHBP synthase; EC=4.1.99.12; RecName: Full=GTP cyclohydrolase-2; EC=3.5.4.25; AltName: Full=GTP cyclohydrolase II;

Gene name

ribBA

FUNCTION: Catalyzes the conversion of D-ribulose 5-phosphate to formate and 3,4-dihydroxy-2-butanone 4-phosphate (By similarity).

FUNCTION: Catalyzes the conversion of GTP to 2,5-diamino-6-ribosylamino-4(3H)-pyrimidinone 5'-phosphate (DARP), formate and pyrophosphate (By similarity).

CATALYTIC ACTIVITY: D-ribulose 5-phosphate = formate + L-3,4-dihydroxybutan-2-one 4-phosphate.

CATALYTIC ACTIVITY: GTP + 3 H(2)O = formate + 2,5-diamino-6-hydroxy-4-(5-phospho-D-ribosylamino)pyrimidine + diphosphate.

COFACTOR: Binds 2 divalent metal cations per subunit. Magnesium or manganese (By similarity).

COFACTOR: Binds 1 zinc ion per subunit (By similarity).

PATHWAY: Cofactor biosynthesis; riboflavin biosynthesis; 2-hydroxy-3-oxobutyl phosphate from D-ribulose 5-phosphate: step 1/1.

PATHWAY: Cofactor biosynthesis; riboflavin biosynthesis; 5-amino-6-(D-ribitylamino)uracil from GTP: step 1/4.

SIMILARITY: In the N-terminal section; belongs to the DHBP synthase family.

SIMILARITY: In the C-terminal section; belongs to the GTP cyclohydrolase II family.

Pfam	PF00926; DHBP_synthase; 1; PF00925; GTP_cyclohydro2; 1;
TIGRFAMs	TIGR00505; ribA; 1; TIGR00506; ribB; 1;

GTP-binding, Hydrolase, Lyase, Magnesium, Manganese, Metal-binding, Multifunctional enzyme, Nucleotide-binding, Riboflavin biosynthesis, Zinc.

GO:0000287; Molecular function: magnesium ion binding.
GO:0003935; Molecular function: GTP cyclohydrolase II activity.
GO:0008270; Molecular function: zinc ion binding.
GO:0008686; Molecular function: 3,4-dihydroxy-2-butanone-4-phosphate synthase activity.
GO:0030145; Molecular function: manganese ion binding.
GO:0009231; Biological process: riboflavin biosynthetic process.

From: RIBBA_BACSU (P17620)
Key		From		To		Description		Condition		FTGroup
NP_BIND		251		255		GTP (By similarity)
NP_BIND		294		296		GTP (By similarity)		E-G-R
REGION		Nter		199		DHBP synthase
REGION		26		27		D-ribulose 5-phosphate binding (By similarity)		R-E
REGION		138		142		D-ribulose 5-phosphate binding (By similarity)		R-x-x-H-T
REGION		200		Cter		GTP cyclohydrolase II
ACT_SITE		328		328		Proton acceptor; for GTP cyclohydrolase activity (Potential)		D
ACT_SITE		330		330		Nucleophile; for GTP cyclohydrolase activity (By similarity)		R
METAL		27		27		Magnesium or manganese 1 (By similarity)		E
METAL		27		27		Magnesium or manganese 2 (By similarity)		E
METAL		141		141		Magnesium or manganese 2 (By similarity)		H
METAL		256		256		Zinc; catalytic (By similarity)		C
METAL		267		267		Zinc; catalytic (By similarity)		C
METAL		269		269		Zinc; catalytic (By similarity)		C
BINDING		31		31		D-ribulose 5-phosphate (By similarity)		D
BINDING		162		162		D-ribulose 5-phosphate (By similarity)		E
BINDING		272		272		GTP (By similarity)		Q
BINDING		316		316		GTP (By similarity)		T
BINDING		351		351		GTP (By similarity)		[TS]
BINDING		356		356		GTP (By similarity)		K
SITE		124		124		Essential for DHBP synthase activity (By similarity)		H
SITE		162		162		Essential for DHBP synthase activity (By similarity)		E

Size range:	388-425 amino acids
Related UniRules:	MF_00178 (RISB); MF_00179 (RIBA)
Template:	P50855 (RIBBA_ACTPL)
Scope:	Bacteria
Fusion:	Nter: None; Cter: <Unknown>
Duplicate:	None
Plasmid encoded:	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.