HAMAP

Accession	MF_00179
Dates	1-JUN-2001 (Created) 18-MAY-2011 (Last updated, Version 21)

Data class

Protein

Predictors

HAMAP; MF_00179; [distribution of match scores in UniProtKB];[seed alignment for MF_00179]

Names

RibA

Identifier

RIBA

Protein name

RecName: Full=GTP cyclohydrolase-2; EC=3.5.4.25; AltName: Full=GTP cyclohydrolase II;

Gene name

ribA

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

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

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

SUBUNIT: Homodimer (By similarity).

SIMILARITY: Belongs to the GTP cyclohydrolase II family.

Pfam	PF00925; GTP_cyclohydro2; 1;
TIGRFAMs	TIGR00505; RibA; 1;

GTP-binding, Hydrolase, Metal-binding, Nucleotide-binding, Riboflavin biosynthesis, Zinc.

GO:0003935; Molecular function: GTP cyclohydrolase II activity.
GO:0008270; Molecular function: zinc ion binding.
GO:0009231; Biological process: riboflavin biosynthetic process.

From: RIBA_ECOLI (P0A7I7)
Key		From		To		Description		Condition		FTGroup
NP_BIND		49		53		GTP (By similarity)
NP_BIND		92		94		GTP (By similarity)		E-G-R
ACT_SITE		126		126		Proton acceptor (Potential)		D
ACT_SITE		128		128		Nucleophile (By similarity)		R
METAL		54		54		Zinc; catalytic (By similarity)		C
METAL		65		65		Zinc; catalytic (By similarity)		C
METAL		67		67		Zinc; catalytic (By similarity)		C
BINDING (Optional)		70		70		GTP (By similarity)		Q
BINDING		114		114		GTP (By similarity)		T
BINDING		149		149		GTP (By similarity)		[TS]
BINDING		154		154		GTP (By similarity)		K

Size range:	192-222 amino acids
Related UniRules:	MF_01283 (RIBBA (supersedes the current rule))
Template:	P0A7I7 (RIBA_ECOLI); O08315 (RIBA_HELPY): [Recover all]
Scope:	Bacteria Archaea
Fusion:	Nter: <ribB-like>, <Unknown>; Cter: None
Duplicate:	None
Plasmid encoded:	None
Comments:	RibA and RibB are fused in some organisms (see MF_01283 for bifunctional RibBA). Some RibA are preceded by a ribB-like domain, which does not seem to code for DHBP synthase activity because it lacks all the residues important for activity. Fused with an unknown N-terminal domain in XYLFA and XYLFT. Possible wrong start in STRCO.