Q26997 (HGXR_TOXGO) Reviewed, UniProtKB/Swiss-Prot

Names and origin

Protein names

Recommended name:
Hypoxanthine-guanine-xanthine phosphoribosyltransferase
Short name=HGPRT
Short name=HGXPRT
Short name=HGXPRTase
EC=2.4.2.-

Gene names

Name:

HPRT

Organism

Toxoplasma gondii

Taxonomic identifier

5811 [NCBI]

Taxonomic lineage

cellular organisms › Eukaryota › Alveolata › Apicomplexa › Conoidasida › Coccidia › Eucoccidiorida › Eimeriorina › Sarcocystidae › Toxoplasma

Protein attributes

Sequence length	230 AA.
Sequence status	Complete.
Protein existence	Evidence at protein level

General annotation (Comments)

Function	Catalyzes the transfer of a ribosyl phosphate group from 5-phosphoribose 1-diphosphate to the N9 of hypoxanthine, guanine or xanthine. Ref.5
Catalytic activity	IMP + diphosphate = hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate. Ref.4 Ref.5 GMP + diphosphate = guanine + 5-phospho-alpha-D-ribose 1-diphosphate. Ref.4 Ref.5 5-phospho-alpha-D-ribose 1-diphosphate + xanthine = (9-D-ribosylxanthine)-5'-phosphate + phosphate. Ref.4 Ref.5
Cofactor	Binds 2 magnesium ions per subunit. The magnesium ions are essentially bound to the substrate and have few direct interactions with the protein. Ref.4
Pathway	Purine metabolism; GMP biosynthesis via salvage pathway; GMP from guanine: step 1/1. Purine metabolism; IMP biosynthesis via salvage pathway; IMP from hypoxanthine: step 1/1. Purine metabolism; XMP biosynthesis via salvage pathway; XMP from xanthine: step 1/1.
Subunit structure	Homodimer at low ionic strength and homotetramer at high ionic strength. Ref.4
Subcellular location	Cytoplasm.
Sequence similarities	Belongs to the purine/pyrimidine phosphoribosyltransferase family.

Ontologies

Keywords
Biological process	Purine salvage
Cellular component	Cytoplasm
Ligand	Magnesium Metal-binding Nucleotide-binding
Molecular function	Glycosyltransferase Transferase
Technical term	3D-structure
Gene Ontology (GO)
Biological_process	GMP salvage Inferred from electronic annotation. Source: UniProtKB-UniPathway IMP salvage Inferred from electronic annotation. Source: UniProtKB-UniPathway XMP salvage Inferred from electronic annotation. Source: UniProtKB-UniPathway purine ribonucleoside salvage Inferred from electronic annotation. Source: UniProtKB-KW
Cellular_component	cytoplasm Inferred from electronic annotation. Source: UniProtKB-SubCell
Molecular_function	hypoxanthine phosphoribosyltransferase activity Inferred from electronic annotation. Source: InterPro metal ion binding Inferred from electronic annotation. Source: UniProtKB-KW nucleotide binding Inferred from electronic annotation. Source: UniProtKB-KW
Complete GO annotation...

Sequence annotation (Features)

Feature key

Position(s)

Length

Description

Graphical view

Feature identifier

Molecule processing

Chain

1 – 230

230

Hypoxanthine-guanine-xanthine phosphoribosyltransferase

PRO_0000139599

Regions

Nucleotide binding

146 – 154

9

GMP

Nucleotide binding

199 – 200

2

GMP

Sites

Active site

150

1

Proton acceptor Ref.4 Ref.5

Metal binding

206

1

Magnesium

Binding site

79

1

GMP

Binding site

178

1

GMP

Binding site

206

1

GMP; via carbonyl oxygen

Experimental info

Mutagenesis

150

1

D → A: Strongly reduced catalytic activity. Ref.4

Secondary structure

1

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230

Helix Strand Turn

Details...

Helix

6 – 8

3

Beta strand

9 – 11

3

Helix

29 – 31

3

Turn

36 – 41

6

Beta strand

44 – 47

4

Helix

49 – 67

19

Beta strand

72 – 78

7

Turn

79 – 81

3

Helix

82 – 98

17

Beta strand

109 – 119

11

Beta strand

122 – 130

9

Helix

134 – 137

4

Beta strand

141 – 152

12

Helix

153 – 163

11

Beta strand

168 – 178

11

Beta strand

189 – 195

7

Beta strand

200 – 202

3

Turn

208 – 213

6

Beta strand

215 – 219

5

Helix

222 – 228

7

Sequences

	Sequence		Length	Mass (Da)
	Q26997 [UniParc]. Last modified November 1, 1996. Version 1. Checksum: C3784254EF96361D	FASTA	230	26,386
	10 20 30 40 50 60 MASKPIEDYG KGKGRIEPMY IPDNTFYNAD DFLVPPHCKP YIDKILLPGG LVKDRVEKLA 70 80 90 100 110 120 YDIHRTYFGE ELHIICILKG SRGFFNLLID YLATIQKYSG RESSVPPFFE HYVRLKSYQN 130 140 150 160 170 180 DNSTGQLTVL SDDLSIFRDK HVLIVEDIVD TGFTLTEFGE RLKAVGPKSM RIATLVEKRT 190 200 210 220 230 DRSNSLKGDF VGFSIEDVWI VGCCYDFNEM FRDFDHVAVL SDAARKKFEK

References

[1]	"Isolation and sequencing of a cDNA encoding the hypoxanthine-guanine phosphoribosyltransferase from Toxoplasma gondii." Vasanthakumar G., van Ginkel S., Parish G. Gene 147:153-154(1994) [PubMed] [Europe PMC] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [MRNA]. Strain: RH.
[2]	"Crystal structures of Toxoplasma gondii HGXPRTase reveal the catalytic role of a long flexible loop." Schumacher M.A., Carter D., Roos D.S., Ullman B., Brennan R.G. Nat. Struct. Biol. 3:881-887(1996) [PubMed] [Europe PMC] [Abstract] Cited for: X-RAY CRYSTALLOGRAPHY (2.4 ANGSTROMS).
[3]	"Crystal structures of the Toxoplasma gondii hypoxanthine-guanine phosphoribosyltransferase-GMP and -IMP complexes: comparison of purine binding interactions with the XMP complex." Heroux A., White E.L., Ross L.J., Borhani D.W. Biochemistry 38:14485-14494(1999) [PubMed] [Europe PMC] [Abstract] Cited for: X-RAY CRYSTALLOGRAPHY (1.65 ANGSTROMS).
[4]	"Crystal structure of Toxoplasma gondii hypoxanthine-guanine phosphoribosyltransferase with bound XMP, pyrophosphate and two Mg2+ ions: insights into the catalytic mechanism." Heroux A., White E.L., Ross L.J., Davis R.L., Borhani D.W. Biochemistry 38:14495-14506(1999) [PubMed] [Europe PMC] [Abstract] Cited for: X-RAY CRYSTALLOGRAPHY (1.6 ANGSTROMS) OF MUTANT ALA-150 IN COMPLEX WITH XMP; PYROPHOSPHATE AND MAGNESIUM IONS, COFACTOR, CATALYTIC ACTIVITY, SUBUNIT, ACTIVE SITE, MUTAGENESIS OF ASP-150.
[5]	"Substrate deformation in a hypoxanthine-guanine phosphoribosyltransferase ternary complex: the structural basis for catalysis." Heroux A., White E.L., Ross L.J., Kuzin A.P., Borhani D.W. Structure 8:1309-1318(2000) [PubMed] [Europe PMC] [Abstract] Cited for: X-RAY CRYSTALLOGRAPHY (1.05 ANGSTROMS) IN COMPLEX WITH MAGNESIUM; PHOSPHORIBOSYLPYROPHOSPHATE AND 9-DEAZAGUANINE, CATALYTIC ACTIVITY, ACTIVE SITE, FUNCTION.

Cross-references

Sequence databases

EMBL
GenBank
DDBJ

U09219 mRNA. Translation: AAA57068.1.

3D structure databases

PDBe
RCSB PDB
PDBj

Entry	Method	Resolution (Å)	Chain	Positions	PDBsum
1DBR	X-ray	2.40	A/B/C/D	1-230	[»]
1FSG	X-ray	1.05	A/C	1-230	[»]
1QK3	X-ray	1.65	A/B/C/D	1-230	[»]
1QK4	X-ray	1.90	A/B/C/D	1-230	[»]
1QK5	X-ray	1.60	A/B	1-230	[»]

ProteinModelPortal

Q26997.

SMR

Q26997. Positions 1-230.

ModBase

Search...

Protocols and materials databases

StructuralBiologyKnowledgebase

Search...

Enzyme and pathway databases

UniPathway

UPA00591; UER00648.
UPA00602; UER00658.
UPA00909; UER00887.

Family and domain databases

InterPro

IPR005904. Hxn_phspho_trans.
IPR000836. PRibTrfase_dom.
[Graphical view]

Pfam

PF00156. Pribosyltran. 1 hit.
[Graphical view]

TIGRFAMs

TIGR01203. HGPRTase. 1 hit.

PROSITE

PS00103. PUR_PYR_PR_TRANSFER. 1 hit.
[Graphical view]

ProtoNet

Search...

Other

EvolutionaryTrace

Q26997.

Entry information

Entry name

HGXR_TOXGO

Accession

Primary (citable) accession number: Q26997

Entry history

Integrated into UniProtKB/Swiss-Prot:	November 1, 1997
Last sequence update:	November 1, 1996
Last modified:	April 3, 2013
This is version 79 of the entry and version 1 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)